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1、White Paper on Survey of Optical Modules in Wireless Fronthaul White Paper on Survey of Optical Modules in Wireless Fronthaul White Paper on Survey of Optical Modules in Wireless Fronthaul White Paper on Survey of Optical Modules in Wireless Fronthaul Version 1.0 June 15,2023 White Paper on Survey o
2、f Optical Modules in Wireless Fronthaul White Paper created and approved by IPEC www.ipec-org.org The International Photonics&Electronics Committee(IPEC)is an international standards organization that is committed to developing open optoelectronic standards and delivering strategic roadmap reports.I
3、PEC focuses on standardizing solutions in optical chips,optical/electrical components,and optical modules.Markets addressed by IPEC include 5G,IoT and AI.The gradual digitalization of these industries and the construction of new infrastructure require standardization.However,current optoelectronic s
4、tandards are reactive,do not pro-actively motivate strategic investments,and do not address all market segments.Therefore,IPEC will look beyond the work of other standards organizations.IPEC will support the optoelectronic industry for the long term,and address un-met needs of its members.IPEC is op
5、en to any interested party who wishes to join.All members have the opportunity to participate in developing all IPEC standards and reports on a non-discriminatory basis.The process of developing these standards and reports is transparent to all members.IPEC is registered in Switzerland.White Paper o
6、n Survey of Optical Modules in Wireless Fronthaul White Paper on Survey of Optical Modules in Wireless Fronthaul Summary This white paper analyzes application scenarios of the next-generation fronthaul solutions and explores standards for 50G optical modules.Keywords Fronthaul,50G,MPI,Dispersion,Sta
7、ndard Working Group:Network Requirements TITLE:White Paper on Survey of Optical Modules in Wireless Fronthaul SOURCE:TECHNICAL EDITOR Name:Feng Jia Company Name:Huawei Technologies Co.,Ltd Email: SOURCE:TECHNICAL EDITOR Name:Sheng Xia Company Name:China Telecommunications Corporation Email: SOURCE:T
8、ECHNICAL EDITOR Name:Li Can Company Name:Huawei Technologies Co.,Ltd Email: White Paper on Survey of Optical Modules in Wireless Fronthaul WORKING GROUP CHAIR Name:Liu Hao Company Name:China Telecommunications Corporation Email: List of Members The following companies were members of this project at
9、 the release of this specification:Company China Telecommunications Corporation China Academy of Information and Communications Technology Huawei Technologies Co.,Ltd.Accelink Technologies Co.,Ltd.HG Genuine Optics Tech Co.,Ltd.Hisense Broadband Multimedia Technologies Co.,Ltd.InnoLight Technology(S
10、uzhou)Ltd.Sitrus Technology EXFO Inc.FiberHome Source Photonics Shanghai Jiao Tong University Document Revision History Rev Date Description 1.0 2023-06-15 Publication of this White Paper.White Paper on Survey of Optical Modules in Wireless Fronthaul Contents Overview.1 1 Challenges and Opportunitie
11、s for 5G Fronthaul Optical Modules.2 1.1 5G Fronthaul Network.2 1.2 Challenges to 5G Fronthaul Optical Modules.2 2 Survey of 5G Fronthaul Optical Networks.3 2.1 Fronthaul Networking.3 2.2 Survey of Fronthaul Optical Links.4 2.2.1 Transmission Distance.4 2.2.2 Link Loss.5 2.2.3 Optical Fiber MPI.6 2.
12、2.4 Transmission Fiber Dispersion.8 2.3 Survey on Optical Modules for Fronthaul.9 2.3.1 Optical Module Types.9 2.3.2 Optical Module Temperatures.10 2.4 Survey on Industry Standards.11 2.4.1 IPEC Standard Evolution of 50G Fronthaul Optical Modules.11 2.4.2 Current State and Evolution of Standards for
13、 50G Fronthaul Optical Modules in China.12 2.4.3 MOPA Standard Progress of 50G Fronthaul Optical Modules.13 2.4.4 Summary of 50G Fronthaul Optical Module Standard Evolution.14 2.5 Survey on the Industry Chain.14 3 Recommendations to Achieve Standardization of Next-Generation Fronthaul Optical Module
14、s.15 3.1 Wireless Fronthaul Rate Evolution and MFH50 Application Scenarios.15 3.2 Recommendations for MFH50 Optical Module Standardization.16 3.2.1 Standards of 50G Dual-Fiber Bidirectional Gray Optics.16 3.2.2 Standards of 50G Single-Fiber Bidirectional Gray Optics.16 3.2.3 Standards of 50G CWDM 6
15、Optical Modules(TBD).16 3.3 MFH50 Encapsulation Protocol.16 3.4 MFH50 Test Standards.18 3.4.1 Eye Pattern Test.18 3.4.2 Rate Switching Setup Time.18 3.4.3 Latency Test.20 3.4.4 Multi-Vendor Test.20 4 Summary and Prospect of Wireless Next-Generation Fronthaul Optical Modules.22 5 Reference.23 White P
16、aper on Survey of Optical Modules in Wireless Fronthaul 1 Overview 5G networks have become a critical component of a nations infrastructure,with many countries already deploying 5G technologies on a large scale.With such mass deployments,there are of course opportunities and challenges.For example,5
17、G enables enhanced Mobile Broadband(eMBB)applications and Internet of Things(IoT)applications(interconnection between devices).However,to support new applications and ultimate user experience,5G must meet specific efficiency and performance requirements,deliver higher user-perceived rates,and provid
18、e higher bandwidths.Centralized RAN(CRAN)facilitates quick 5G deployment.New 5G fronthaul solutions can run on CRAN to provide denser connections,less power consumption,and simpler fronthaul architectures.This background can create new wireless access topologies.New fronthaul solutions promote the c
19、onstruction of the next-generation wireless networks and maximize the multiplier effect of wireless networks in various fields.Next-generation fronthaul solutions are expected to be put into commercial use between 2024 to 2026,and to ensure 6G-oriented evolution,the International Photonics&Electroni
20、cs Committee(IPEC)has set up the next-generation mobile fronthaul 50G(MFH50)project.This white paper analyzes application scenarios of the next-generation fronthaul solutions and explores standards for 50G optical modules.White Paper on Survey of Optical Modules in Wireless Fronthaul 2 1 Challenges
21、and Opportunities for 5G Fronthaul Optical Modules 1.1 5G Fronthaul Network 5G fronthaul has become an important part of 5G networks.Fronthaul networks are classified into distributed RAN(DRAN)and CRAN.The two types of networks will retain even after an upgrade to the next-generation wireless networ
22、ks.To support the rising number of sites and carriers,more optical fiber resources must be available for fronthaul.5G fronthaul optical modules,which are currently available in many forms,typically run rates of 25G and 10G.Conventional optical modules include dual-fiber bidirectional gray optics,but
23、 future solutions will save on optical fiber resources.New solutions include single-fiber bidirectional(BIDI)and passive wavelength division multiplexing(WDM),the latter of which is divided into coarse wavelength division multiplexing(CWDM),LAN wavelength division multiplexing(LWDM),medium wavelengt
24、h division multiplexing(MWDM),and dense wavelength division multiplexing(DWDM).In addition,semi-active and active WDM solutions are planned for specific scenarios.As a variety of different 25G WDM optical module-based solutions are currently available,it is recommended that next-generation fronthaul
25、 optical module solutions be narrowed down,with performance,costs,and industry chain maturity considered.Due to the increase in the required air interface bandwidth in scenarios where massive MIMO base stations with more channels,U6G base stations,or mmWave base stations are used,future fronthaul ne
26、tworks will require larger bandwidth.It is expected that next-generation 5G fronthaul optical modules will be developed to provide higher rates while retaining the existing number of ports and optical fiber resources.1.2 Challenges to 5G Fronthaul Optical Modules The rise of CRAN deployment requires
27、 a longer fiber length,fewer backbone optical fibers,and higher rates.Next-generation 5G fronthaul must meet diverse bandwidth,optical module performance,optical link quality(multipath interference penalty or MPI penalty,and dispersion penalty),and power consumption requirements.Ambient temperature
28、Fronthaul devices work in many complex environments.In DRAN,baseband units(BBUs)are typically deployed indoors(in equipment rooms or cabinets)or outdoors.In CRAN,BBUs are deployed in central equipment rooms and remote radio units(RRUs)/active antenna units(AAUs)are deployed outdoors(on towers,poles,
29、or walls),and as such,optical modules must be able to withstand extreme environmental conditions.Power consumption Optical modules have specific operating temperature ranges,and their power consumption must meet the requirements of the air-cooling system for the BBU and the natural heat dissipation
30、system for RF modules.Link budget Although CRAN allows data to be transmitted over greater fiber distances,the challenge arises in keeping costs low and yield rates high.The TX optical power and receiver sensitivity of optical modules must be considered during link power budget.Compared with 25 Gb/s
31、 non-return zero(NRZ),50 Gb/s four-level pulse-amplitude modulation(PAM4)requires higher receiver sensitivity.Given the same link budget,the TX optical power of 50G optical modules must be increased.Optical fiber quality White Paper on Survey of Optical Modules in Wireless Fronthaul 3 Increasing fro
32、nthaul rates and using PAM4 typically cause an increase in dispersion and MPI penalty on fiber links.CWDM is the mainstream solution used in CRAN in China.The dispersion penalty can be large for optical modules with a wavelength of 1351 nm or 1371 nm.One way to overcome this challenge is to apply di
33、spersion compensation through optical digital signal processor(oDSP)or other innovative methods.In wireless fronthaul links,engineering deployments cannot meet the high cleanliness(low reflectance)requirement defined by IEEE,and designs of 50G optical modules must balance TX optical power,RX sensiti
34、vity,and dispersion and MPI penalty.Multi-rate In 5G,different split solutions require varying rates.For example,SFP 25G optical modules need to support two rates,24.33 Gbit/s(CPRI)and 25.78 Gbit/s(eCPRI),while enhanced models,such as SFP 50G optical modules,need to support 50.13504 Gbit/s(CPRI)and
35、53.125 Gbit/s(eCPRI).To suit the fronthaul interface of the existing BBUs/RF modules,SFP 50G optical modules must be compatible with the rate of 25G.Encapsulation protocol To support intelligent operations and maintenance(O&M)features,registers such as those related to signal-to-noise ratio(SNR),pow
36、er-on duration,and multi-rate compatibility need to be added for wireless fronthaul optical modules.The current encapsulation standard,SFF 8472,cannot meet the current demands,and as such,SFP 50G optical modules must consider the inventory software versions and future evolution requirements.2 Survey
37、 of 5G Fronthaul Optical Networks This white paper surveys wireless fronthaul scenarios and summarizes MFH50,including its requirements,specifications and suggestions of each work group.The survey data includes the inventory information about optical modules(mostly on networks using LTE/NR base stat
38、ions)of certain offices of three tier-1 Chinese operators and statistics on related fronthaul links.The survey data relates to hundreds of thousands of links and nearly one million optical modules in provinces in China.2.1 Fronthaul Networking Figure 1 shows DRAN and CRAN fronthaul networks.In DRAN,
39、the BBU and RF modules are typically deployed at the same site,leading to a short transmission distance.In certain cases,RF modules are deployed far from the BBU or RF modules are cascaded.As such,gray optics for short-distance transmission are typically used.In CRAN,BBUs are centralized in an equip
40、ment room and RF modules are deployed far from the BBUs.This results in a long transmission distance,and long optical fibers have to be used between the BBUs and RF modules.As such,gray optics for long-distance transmission and WDM optical modules are typically used.WDM solutions include passive WDM
41、,active WDM and semi-active WDM.Passive WDM is cost-effective and easy to deploy;active WDM supports high-reliability and proactive O&M and monitoring,but is difficult to deploy;and semi-active WDM uses passive multiplexers on the AAU side to simplify deployment,and active devices on the BBU side to
42、 implement O&M.The semi-active WDM solution combines passive WDM and active WDM,to deliver competitive advantages but at a higher price point.White Paper on Survey of Optical Modules in Wireless Fronthaul 4 Figure 1 DRAN and CRAN 2.2 Survey of Fronthaul Optical Links DRAN and CRAN support different
43、optical link distances.The optical link conditions for deploying gray optics and WDM optical modules are also different.For example,long link distances are supported when WDM optical modules are used,with multiplexers and demultiplexers added at remote sites and central equipment rooms.In this case,
44、the link differences between WDM optical modules and gray optics must be considered during optical module design.This white paper analyzes fronthaul optical links,including the transmission distance and link loss,and the influence of MPI penalty and dispersion penalty as they are key factors that af
45、fect link budget and optical link quality.2.2.1 Transmission Distance The fiber transmission distance can be calculated using transmission delay,though the two factors do not influence the processing capabilities of wireless and transmission equipment.Figure 2 Measurement of the transmission distanc
46、e of an optical fiber In Figure 2,a measurement signal is transmitted from the BBU to an RRU over an optical fiber,and then loops back to the BBU.The speed of light over optical links is about 200000 km/s,and the fiber length related to the fronthaul link is measured based on transmission delay as f
47、ollows:White Paper on Survey of Optical Modules in Wireless Fronthaul 5 =()200000 2 is the time when the measurement signal is transmitted;is the duration the RRU chip processes the measurement signal;and is the time when the measurement signal loops back to the BBU.Figure 3 shows live network stati
48、stics about fiber distances at certain offices.Detailed descriptions are as follows:In terms of networking,about 70%of all direct fiber links using gray optics do not exceed 2 km.In DRAN,gray optics for short-distance transmission are typically used.By comparison,CRAN typically uses WDM optical modu
49、les(with convergence)with fiber link distances of 2 km to 6 km.Such a transmission distance is longer than that when gray optics are used.In certain cases,CRAN uses gray optics for direct fiber links.In terms of transmission distances,the fiber link distance is typically within 10 km for fronthaul u
50、sing gray optics or WDM optical modules,though this can exceed 10 km if needed.Figure 3 Live network statistics about fiber link distances at certain offices 2.2.2 Link Loss The main sources of link loss over an optical link are the optical fibers,connectors,maintenance,multiplexers/demultiplexers(p
51、resent in WDM),dispersion,and MPI(Figure 4).With the rise of fronthaul rates,the dispersion penalty and MPI penalty have an increasing impact on link loss.The link loss can be calculated based on the difference in the TX and RX optical power of optical modules between the BBU and RF modules.Figure 4
52、 Link budget for CWDM optical modules Figure 5 and Figure 6 show live network statistics about link loss at certain offices.The main takeaways are as follows:White Paper on Survey of Optical Modules in Wireless Fronthaul 6 Given the same fiber length,the average link loss when WDM optical modules ar
53、e used is approx.3 dB greater than that when gray optics are used,due to multiplexers/demultiplexers and connectors on the colored fiber links.Gray optics support link distances up to 2 km,with an average link loss of approx.4 dB,which is relatively low.WDM optical modules support link distances of
54、between about 2 km and 6 km,with an average link loss of approx.10 dB,which is relatively high.Figure 5 Live network statistics about link loss at certain offices According to the distribution of link loss when WDM optical modules are used with link distances of between 2 km and 3 km and between 7 k
55、m and 8 km,different links of distances in the same range have varying quality.In the case of a large link loss,an optical link is subject to potential risks even if the RX optical power alarm threshold has not been reached.In this case,it is necessary to rectify any link issues to prevent the link
56、from deteriorating further and impacting services.Figure 6 Distribution of link loss with WDM optical modules under different link distance ranges 2.2.3 Optical Fiber MPI The multiple connection points in an optical link reflect certain optical signals,in which light can be reflected again at a conn
57、ection point,and as such,an interference signal is generated and transmitted in the same direction as the original signal.At the receive end,the interference signal is superimposed onto the original signal.This propagation means that the receiver receives both wanted and unwanted signals and therefo
58、re the SNR is degraded and system transmission performance deteriorates.MPI occurs when the interference signals generated over multiple paths are superimposed onto the original signals at the receive end.The impact of MPI depends on the strength of the interference signals when they are superimpose
59、d onto the original signals and the original signals tolerance to the interference signals.The main influencing factors include the number and reflectance of connection points,and polarization direction of interference signals,whereby White Paper on Survey of Optical Modules in Wireless Fronthaul 7
60、the larger the reflectance,the larger the number of connection points,and the more the alignment between the polarization of the interference and original signals,the greater the MPI impacts.In addition,other factors include phases of interference signals,interference signal loss due to transmission
61、 through intermediate connectors,and amplitudes and extinction ratios of the original signals.The MPI penalty is indicated by the changes in the quality factor of eye pattern at the receive end,the ratio of the total power of all reflected signals to that of the original signals,or the changes in re
62、ceiver sensitivity under the same bit error rate(BER).The IEEE 802.3 Ethernet standards state that the reflectance of each connector must be less than 35 dB when there are six connectors.To limit MPI risks,it is recommended that simulations run on general link model to convert the MPI penalty to lin
63、k loss and apply forward error correction(FEC)to improve tolerance.Figure 7 Quantitative analysis of MPI Figure 7 shows the quantitative analysis of MPI in an optical link from three aspects.Data from hundreds of links in an MFH survey,such as the number of connectors,reflectance,and distance,is use
64、d as the input for subsequent tests in research and development(R&D)environments and MPI simulations.The live network data is used for typical fronthaul scenarios in R&D environments to test the impact of MPI penalty on actual networks and related MPI changes under different conditions.Based on the
65、MPI principle,the connector-specific parameters are determined using real-link MPI simulation models to accurately evaluate the link loss due to large reflection events.The R&D test and simulation results can be mutually calibrated to obtain a more accurate link MPI penalty.A typical 5G fronthaul C-
66、RAN deployment uses six connectors(ODFs and multiplexers/demultiplexers on both sides).According to IEEE 802.3,the reflectance of each connector must be less than 35 dB,but this survey at certain offices finds 32.8%of live-network connectors on high-risk fronthaul links have a reflectance of greater
67、 than 35 dB,in addition to 29%greater than 30 dB and 9.8%greater than 20 dB.We can ascertain that for the deteriorated connectors on some fronthaul links,the reflectance is greater than 20 dB,which means the equivalent MPI reflectance is likely greater than 30 dB,causing MPI risks to arise in fronth
68、aul links.A typical equivalent MPI test on the live network requires a delay fiber,variable optical attenuator(VOA),and polarization controller.The preliminary test result of the survey suggests the maximum equivalent MPI reflectance tolerated by optical modules is approximately 33 dB.Table White Pa
69、per on Survey of Optical Modules in Wireless Fronthaul 8 1 lists the MPI penalty simulation using fronthaul simulation models.To improve the accuracy of MPI penalty,factors that influence the simulation model like the number of connectors,typical reflectance of connectors,and connector positions wil
70、l be further calibrated based on live network surveys and lab tests.Table 1 MPI simulation results Simulation Configuration ROP(dBm)ER(dB)MPI Penalty(dB)No MPI 10.16 3.5/6 x(35 dB)10.08 3.5 0.08 6 x(33 dB)10.04 3.5 0.12 6 x(29 dB)9.76 3.5 0.40 6 x(26 dB)8.99 3.5 1.17 Note:Simulation OMA and ROP para
71、meter settings at 2E-4 BER 2.2.4 Transmission Fiber Dispersion Dispersion is a common issue in fronthaul links.It mainly comes in the form of material dispersion but also in waveguide dispersion.Fiber dispersion causes pulse broadening,lower peak power to signals in the time domain,and a decrease in
72、 extinction ratio and SNR.The zero-dispersion point of G.652 fibers is near the 1310 nm wavelength region.Table 2 lists the dispersion in a typical fronthaul application scenario(10 km).For the 6-wavelength CWDM,the 1371 nm wavelength records the highest dispersion(36 ps/nm to 66.2 ps/nm)for a 10-km
73、 fiber.Table 2 Typical fronthaul dispersion(for a 10-km fiber)Dispersion 6-wavelength CWDM 1271 nm 1291 nm 1311 nm 1331 nm 1351 nm 1371 nm Minimum 10-km dispersion(ps/nm)59.4 38.5 18.5 0.5 18.6 36.0 Maximum 10-km dispersion(ps/nm)21.5 2.3 16.0 33.4 50.2 66.2 Table 3 lists the mainstream dispersion c
74、ompensation solutions.The dispersion fiber/grating solution is difficult to implement because it requires prior measurements of the dispersion of the fronthaul link,and its parameters such as the length of the dispersion fiber/grating need to be tailored for a site and further configured for the opt
75、ical modules.The digital signal processor(DSP)compensation solution can compensate for electrical dispersion,but the compensation capability varies between vendors and requires prior tests and surveys.Generally,the 50G CWDM optical module employs a directly modulated laser(DML),and therefore the ext
76、ernal modulation solution(EML/MZM)can be used to reduce the chirp effect of lasers and subsequently the dispersion penalty.Another solution,the micro-ring dispersion compensation solution,provides a theoretical compensation of 720 ps/nm,though this research is still incomplete.White Paper on Survey
77、of Optical Modules in Wireless Fronthaul 9 In general,the DSP compensation solution may provide the most competitive advantages.Table 3 Mainstream dispersion compensation solutions Solution Dispersion fiber/grating oDSP compensation Chirp-free external modulation Micro-ring dispersion compensation C
78、ompensation Amount Customized compensation amount appr.10 ps/nm(evaluated based on vendor-specific tests)appr.15 ps/nm appr.720 ps/nm Size Large Medium(integrated into oDSP)Small Small Optical Insertion Loss 1.X to 3 dB None appr.1 dB appr.1 dB Maturity Mature Mature The 50 Gb/s MZM solution support
79、s mass production.Under research 2.3 Survey on Optical Modules for Fronthaul To understand the evolution trends of next-generation fronthaul optical modules,this survey focuses on the optical module type and temperature,with further market analysis used for the different types of optical modules.The
80、 optical module temperature is a key indicator in design of optical modules,as it influences power consumption,cost,and base station hardware compatibility.2.3.1 Optical Module Types Current optical modules are tailored for various 5G fronthaul setups.The evolution trends of next-generation fronthau
81、l optical modules are still under research.Figure 8 shows the statistics about the types of optical modules on the live network for an operator in the China region.The survey data covers a period starting from before 2019 to the present day where 5G is now deployed on a large scale.Statistics indica
82、te that gray optics are the mainstream type of optical modules for fronthaul,owing to their strengths in flexibility and easy deployment,and are expected to be a mainstay in the next-gen high-speed 50G fronthaul market.The WDM solution is available for organizations to overcome insufficient CRAN fib
83、er resources.Currently,25G CWDM optical modules account for a large share in the WDM market.A small number of 10G CWDM optical modules will be used in small-bandwidth scenarios.It is estimated that CWDM optical modules will account for a large share in the 50G WDM market.Other WDM solutions are unde
84、r exploration.White Paper on Survey of Optical Modules in Wireless Fronthaul 10 Figure 8 Distribution of optical module types for an operator in the China region 2.3.2 Optical Module Temperatures Fronthaul optical modules are deployed in complex and diversified environments.The temperatures of optic
85、al modules vary greatly with regions,seasons,and time intervals.This temperature difference further affects power consumption and performance.The operating and startup temperatures of optical modules must meet industrial-grade specifications,and therefore a long-term survey and analysis on optical m
86、odule temperatures is required.1.Operating temperatures of optical modules The operating temperatures of optical modules are sensitive to their environments.Usually,high operating temperatures result in poor performance and even fronthaul link faults,affecting services.Figure 9 shows the live networ
87、k statistics about operating temperatures of optical modules from two offices in September 2022.Optical modules have an operating temperature range between 0C to 85C,and normally 20C to 50C,meeting the requirements of industrial-grade optical modules.The operating temperatures of optical modules on
88、the BBU side are generally lower than those on the RF side.The ambient temperatures of optical modules on the BBU side are determined by equipment room environments and the fan speed policies of the cabinets,while those on the RF side are determined by the outdoor environments and the power consumpt
89、ion of RF modules.The operating temperatures of optical modules at southern offices generally differ from those at northern offices in China,due to geographical regions and seasons.Currently,optical module temperatures are surveyed at certain offices in China.In future studies,more offices across a
90、wide range will be selected to obtain more complete and long-term data statistics regarding the operating temperatures.White Paper on Survey of Optical Modules in Wireless Fronthaul 11 Figure 9 Live network statistics about operating temperatures of optical modules at certain offices in September 20
91、22 2.Startup temperatures of optical modules The startup temperatures of optical modules are also a key indicator in extreme,low-temperature environments.Especially,optical modules need to be restarted multiple times in such environments to save energy for base stations.The startup temperatures of o
92、ptical modules will be further investigated and analyzed.2.4 Survey on Industry Standards 2.4.1 IPEC Standard Evolution of 50G Fronthaul Optical Modules In September 2021,the IPEC initiated the MFH50 standard project,focusing on single-channel 50G optical links in mobile fronthaul technologies.The I
93、PEC MFH50 research project focuses on optoelectronic components and engineering deployment.The research works on optoelectronic components include optoelectronic parameters of optical modules,optical parameters of passive multiplexers and demultiplexers,low power consumption technology of optical mo
94、dules,and O&M features of optical modules and fronthaul links.The research works on engineering deployment include the fronthaul link quality and optimized fronthaul link engineering solutions.Big data analysis on the existing fronthaul optical link parameters and operating temperatures of optical m
95、odules is expected to enable faster and higher-quality deployment of MFH50 optical modules.The draft of the standards for 50G SFP gray optics(including BIDI)was completed in April 2023,with those for CWDM 6-based 50G fronthaul optical modules set to be improved and released in the future.Other WDM s
96、olutions are under exploration.Figure 10 Roadmap of the IPEC MFH50 project White Paper on Survey of Optical Modules in Wireless Fronthaul 12 2.4.2 Current State and Evolution of Standards for 50G Fronthaul Optical Modules in China 2.4.2.1 Current State China Communications Standards Association(CCSA
97、)is the standards body in China.In 2020 and 2021,CCSA released the technical specifications for 50G dual-and single-fiber bidirectional gray optics,namely,50Gb/s PAM4 Modulation Pluggable Transceiver(YD/T 3713-2020)(0.1 km/2 km/10 km/40 km)and Single Fiber Bi-Directional(BIDI)Optical Transceiver Mod
98、ule-Part3:50Gb/s(YD/T 2759.3-2021)(10 km/20 km)(https:/ wireless fronthaul scenarios,main wireless equipment can be upgraded by replacement of 25G NRZ optical modules with 50G PAM4 optical modules.However,the current standards for 50G optical modules are incompatible with those for 25G optical modul
99、es in terms of data rate,transmission distance,wavelength range,transmit/receive optical power,receiver sensitivity,and link budget.This incompatibility affects the 50G optical module solution.Currently,CCSA has not defined the standards for fronthaul 50G optical modules,which cannot be used in fron
100、thaul scenarios.In this background,the current standards for fronthaul 50G optical modules must be customized to suit the fronthaul application scenarios.In December 2022,CCSA began research into 50G optical modules for fronthaul,with the standard for SFP gray(including BIDI)optics currently under r
101、evision and that for WDM optical modules in development for technical solutions.Research on the evolution of 25G solutions(such as previous-generation CWDM)for WDM optical modules will continue,with consensus from operators across the industry chain.The research report is expected to be officially r
102、eleased in 2023 or 2024.Research into fronthaul 50G optical modules will focus on WDM optical modules,dual small form-factor pluggable(DSFP),management enhancement,and test standards.In the research,a survey on fronthaul optical modules and links as well as channel penalty analysis will be conducted
103、,and WDM optical module solutions will be proposed.In the fronthaul link survey,the transmit optical power and receiver sensitivity which have impacts on link budgets must be studied and re-defined to ensure compatibility between optical module standards.In addition,attentions should be paid to the
104、encapsulation and electrical parameters of optical modules,and the power supply to optical modules from devices as well as heat dissipation should match to reduce compatibility risks.Further,the optical module management interface must support optical module diagnosis,rate switching,and optical link
105、 detection.Performance tests and platforms from different vendors must use a consistent framework to ensure standardization.2.4.2.2 Evolution Optical module technologies are gradually developing towards higher rates and higher integration.In fronthaul networks,the optical module rate has evolved fro
106、m 10 Gb/s(4G CPRI ports)to 25 Gb/s(5G eCPRI port),and will continue to increase to 50G or higher.Currently,the following standards have been released:10G Duplex/BIDI/CWDM 6:SFP/SFP+optical transceiver module between BBU and RRU for base station interconnecting(YD/T 3131-2016)25G Duplex:Enhanced SFP
107、transceiver(SFP+)used in communication.Part 2:25 Gbit/s(YD/T 3125.2-2019)25G BIDI:(Single fiber bidirectional optical transceiver module Part 2:25Gb/s)(YD/T 2759.2-2020)25G CWDM:(25Gb/s wavelength division multiplexing(WDM)optical transceiver module Part 1:CWDM)(YD/T 4019.1-2022)White Paper on Surve
108、y of Optical Modules in Wireless Fronthaul 13 25G LWDM:(25Gb/s wavelength division multiplexing(WDM)optical transceiver module Part 2:LWDM)(YD/T 4019.2-2022)25G DWDM:(25Gb/s wavelength division multiplexing(WDM)optical transceiver module Part 3:DWDM)(YD/T 4019.3-2022)25G MWDM:(25Gb/s wavelength divi
109、sion multiplexing(WDM)optical transceiver module Part 4:MWDM)(YD/T 4019.4-2022)50G Duplex:(50Gb/s PAM4 modulated optical transceiver module)(YD/T 3713-2020)50G BIDI:(Single fiber first optical transceiver module 3 parts:50Gb/s)(YD/T 2759.3-2021)The 10G/25G-to-50G optical module evolution causes key
110、performance parameters to change,especially in the transmit and receive optical power ranges,OMA receiver sensitivity,and link budget.Existing standards suggest a link budget of 6.9 dB,11.2 dB,and 10 dB for 50G,10G,and 25G duplex and BIDI modules,respectively.A 50G optical module has higher channel
111、loss and reflection penalty during signal transmission than a 25G optical module,and therefore must have a higher link budget to support application scenarios of 25G optical modules.However,the link budget of the existing 50G standard cannot meet requirements.The link budget is determined by the tra
112、nsmit optical power and OMA receiver sensitivity.The new standard will increase the link budget by adjusting the transmit optical power.In addition,50G optical modules must be compatible with previous-generation modules in terms of wavelength range,transmission distance,rate,and temperature.Moreover
113、,revisions must be made to the CWDM multiplexer/demultiplexer standard,dual-channel extended application scope,and module color label specifications to extend applications of the new 50G optical module standards.Currently,Chinese operators adopt the CWDM solution for the mainstream fronthaul optical
114、 modules in their 5G CRAN deployment.IPEC MFH50 explores the compatibility of lasers and passive components like multiplexer/demultiplexer modules with previous-generation solutions.To conclude,the performance indicator and component specifications of 50G optical modules need to be supplemented and
115、revised during the formulation of 50G fronthaul standards.2.4.3 MOPA Standard Progress of 50G Fronthaul Optical Modules In June 2021,the Mobile Optical Pluggables Alliance(MOPA,an organization including Ericsson,Nokia,Coherent,Lumentum,and Sumitomo Electric)released Technical Paper-Version 1.0,which
116、 provided 10G/25G blueprints.In March 2022,Technical Paper-Version 1.1 was released to cover the 50G blueprint.In the applicable blueprint tables,references to existing optical layer interface standards were included.This was further updated to Version 2.1(Papers and Presentations|MOPA Alliance(mopa
117、-alliance.org)in March 2023,which adds a framework for 2 km and 10 km RU-DU direct parallel fibers,dual and BIDI fiber blueprints in section 7.2 DRAN Optical Blueprints.As specified in the blueprints,the standards for 50G duplex and BIDI optical modules(2 km/10 km)are IEEE 802.3-2022,Clauses 139&160
118、(IEEE SA-The IEEE Standards Association-Home)and ITU-T G.9806(Amend 2)(https:/www.itu.int/rec/T-REC-G.9806).This document describes the optical and electrical specifications,test standards,and test methods for 50G optical modules(5 km/10 km/40 km).Also,Technical Paper-Version 2.1 indicates that 50G
119、fronthaul WDM solutions and technologies will evolve continuously,including LWDM and DWDM.These solutions can support long-distance transmission and mitigate dispersion,but are currently expensive and incompatible with the mainstream SFP 25G CWDM optics of Chinese operators,hindering its uptake in g
120、lobal deployments.Such conversion also requires a new industry chain,which means significant investment and expertise.In addition,the specifications of 50G fronthaul optical modules in IEEE 802.3-2022,such as the wavelength range and transmission distance,are different from those in China.Therefore,
121、new standards need to be formulated for new scenarios.White Paper on Survey of Optical Modules in Wireless Fronthaul 14 2.4.4 Summary of 50G Fronthaul Optical Module Standard Evolution The current standards for mainstream 50G fronthaul optical modules in the industry still lack the rationality of pe
122、rformance parameters and compatibility between generations,and these standards need to be further optimized to cover wider application scope and consistency.The IPEC MFH50 standard aims to address the preceding problems and will cover technical fields such as single-and dual-fiber bidirectional gray
123、 optics and WDM optical modules,and adapt to cost efficiency and evolution trends.MFH50 research is a joint venture by IPEC members including operators,vendors(equipment,optical module,electrical chips),and research institutes.This project will continue to focus on problems and challenges in frontha
124、ul scenarios and promote standardization and innovation in the fronthaul optical module field.2.5 Survey on the Industry Chain The industry chain of 50G dual-fiber bidirectional gray optics has taken shape.As for optical chips,50G optical modules use the PAM4 modulation format,which significantly en
125、hances the non-linear effect of lasers,and this issue can be reduced by increasing the bandwidth or optimizing inband flatness.Multiple chip vendors can supply optical chips in batches,such as Lumentum,Sumitomo,Macom,Mitsubishi,Accelink,and Yuanjie.For electrical chips,two solutions are available,in
126、cluding the DSP and clock and data recovery(CDR).DSP vendors like Marvell,Credo,and Chengke Microelectronics have launched driver-integrated DSP chips for 5G fronthaul.CDR vendors include Semtech and Macom,the former of which has launched driver-integrated CDR chips for 5G fronthaul,while the latter
127、s processors are under development.By April 2023,mainstream Chinese optical module vendors produced samples for fronthaul-oriented 50G dual-fiber bidirectional optical modules,which have passed the preliminary performance test and verification.Table 4 50G dual-fiber bidirectional gray optics solutio
128、n Form Factor Operating Distance Center Wavelength Modulation Format Electrical Interface Optical Chip Electrical Chip SFP56 10 km 1310 nm PAM4 1 x 50G PAM4 DFB+PIN CDR/DSP Like the 25G BIDI optical modules,50G BIDI optical modules also use the 1270 nm/1330 nm WDM solution.50G BIDI optical modules s
129、ave on optical fiber resources and deliver desirable latency symmetry while sharing the industry chain of 50G dual-fiber bidirectional optical modules.Currently,50G BIDI optical modules are developed based on the 50G dual-fiber bidirectional optical module solution,but with slower development.Table
130、5 50G BIDI optical module solution Form Factor Operating Distance Center Wavelength Modulation Format Electrical Interface Optical Chip Electrical Chip SFP56 10 km 1270/1330 nm PAM4 1 x 50G PAM4 DFB+PIN CDR/DSP Research into 25G xWDM optical modules is the catalyst for new industry solutions that pr
131、ovide WDM optical modules with higher rates.The research on 50G 6-wavelength CWDM optical White Paper on Survey of Optical Modules in Wireless Fronthaul 15 modules has progressed the most.The same wavelength scheme applies to both 50G and 25G 6-wavelength CWDM optical modules.In terms of optical chi
132、ps,50G CWDM optical modules can reuse the lasers of their 25G counterparts.However,due to the use of PAM4,the required link budget increases,posing higher requirements on the transmit optical power of lasers.As such,the transmit optical efficiency and yield rate of lasers need to be further optimize
133、d.In terms of electrical chips,the CDR or DSP,which is used in 50G gray optics,can also be used in 50G CWDM optical modules.Dispersion penalties vary with wavelengths.Given that CWDM optical modules have a wide wavelength span,the industry has begun to explore the possibility of coexistence of the t
134、wo solutions to achieve the optimal cost-effectiveness.The technical evaluation result as of April 2023 shows that oDSP has performance advantages in the CWDM optical module solution.In addition,the silicon photonics solution is also used for 50G CWDM optical modules,with leading dispersion specific
135、ations indicated by the test data.To date,the industry chain of different types of 50G optical modules is mature,and will harness the development of 50G fronthaul technologies.For its part,IPEC will work with industry partners to develop a consensus on the future optics field,and promote standardiza
136、tion and industrialization that solve the challenges of fronthaul scenarios.3 Recommendations to Achieve Standardization of Next-Generation Fronthaul Optical Modules 3.1 Wireless Fronthaul Rate Evolution and MFH50 Application Scenarios The 5G radio frequency bands are classified into mid-band(sub-6
137、GHz)and high-band(above 6 GHz).In the China region,the 2.6 GHz(160 MHz bandwidth)and 3.5 GHz(200 MHz bandwidth)frequency bands are typically deployed.With eCPRI split,the 50 Gb/s bandwidth is required for wireless fronthaul.Assume that three AAUs are deployed for a site,as shown in Figure 11.If 25G
138、SFP optical modules are used,then two groups of CWDM optical modules(six in total)and two CWDM multiplexer/demultiplexer modules are separately required on the RF and BBU sides,and two feeder fibers are required for BBU-RF connection.The deployment using 50G SFP optical modules uses half the require
139、d optical modules and optical fibers,and reuses legacy multiplexer/demultiplexer modules.Figure 11 Wireless fronthaul evolution solution White Paper on Survey of Optical Modules in Wireless Fronthaul 16 50G RF modules need to support both CPRI and eCPRI rates.Considering PCS encoding and FEC type se
140、lection,50G SFP optical modules need to be compatible with the rates listed in Table 6.Table 6 Rates that need to be supported by 50G SFP optical modules Standard Rate Protocol PCS encoding:257/256,66/64 FEC encoding:KP=544/514,KR=528/514 53.1G eCPRI 50G x 257/256 x 544/514=53.125 Gb/s 50.1G CPRI 96
141、 x 491.52M x 257/256 x 544/514=50.13504 Gb/s 25.78G eCPRI 25G x 257/256 x 528/514=25.78125 Gb/s 24.33G CPRI 48 x 491.52M x 66/64=24.33024 Gb/s 3.2 Recommendations for MFH50 Optical Module Standardization The IPEC initiated the research on MFH50 standards in September 2021,and has completed the draft
142、 of the SFP gray optics(duplex&BIDI)standards by April 2023.The optical parameters,management interfaces,and test methods of 50G gray optics(duplex&BIDI)have been discussed and approved by the IPEC.Future discussions will cover the link budget,MPI,and dispersion of 50G gray optics(duplex&BIDI),the f
143、iber optic cabling model,EMC and safety regulations,as well as WDM optical modules.Related drafts 50 Gb/s Duplex BIDI PMD Implementation Agreement D2.0 and MFH50 management interface V0.1 for SFP gray optics(duplex&BIDI)standards are available on the IPECs official website.For details,register and d
144、ownload at https:/www.ipec-std.org/data-download.This section provides recommendations for standardization of 50G optical modules,including 50 Gb/s gray,BIDI,and CWDM 6 optical modules.3.2.1 Standards of 50G Dual-Fiber Bidirectional Gray Optics For details,the MFH50 standard project is developing re
145、lated standards and specifications.3.2.2 Standards of 50G Single-Fiber Bidirectional Gray Optics For details,the MFH50 standard project is developing related standards and specifications.3.2.3 Standards of 50G CWDM 6 Optical Modules(TBD)The WDM optical module standards of MFH50 are in research.3.3 M
146、FH50 Encapsulation Protocol The new features introduced in 50G SFP optical modules increase the requirements for registers,such as those related to multi-rate compatibility,rate switching time,and optical fiber sensing.Based on SFF-8472 and Common Management Interface Specification(CMIS),new interfa
147、ces are added to provide the following functions:1.Rate set reporting White Paper on Survey of Optical Modules in Wireless Fronthaul 17 Fronthaul optical modules need to support different rates.The main device requires that optical modules be capable of rate set reporting,so that the optical modules
148、 can be properly configured based on the reported rate set.SFF-8472 provides the Application Select Table function,in which each application is assigned a unique application code,including the protocol name,working rate,and modulation format(NRZ or PAM4).50G optical modules can be integrated with th
149、e Application Select Table function to report the supported rate set.2.Delivery of the precise rate during switching Both 25G and 10G optical modules use the NRZ modulation format.During rate switching,only the SerDes rate of the electrical interface or the working rate of the optical interface need
150、s to be switched.In this way,the optical module can lock the rate and switch to the new rate quickly.50G optical modules adopt PAM4 and CDR or DSP technology.Both electrical and optical signals have three decision levels,which can be obtained through training and learning.During rate switching,the C
151、DR or DSP chip needs to obtain the accurate working rate and code pattern to facilitate quick training and learning.With the rate set reporting function,the main device delivers the application code to the optical module that contains the accurate working rate and code pattern required for rate swit
152、ching.3.Reporting of rate switching setup time The rate switching setup time starts when the main device issues a rate switching command to the optical module and ends when the optical module locks the channel and outputs the corresponding signal.The setup time assumes that the signals input into th
153、e optical module meet signal quality requirements in the protocol.The setup time includes electrical-optical conversion(egress)channel setup time and optical-electrical conversion(ingress)channel setup time.Both 10G and 25G optical modules adopt the NRZ code pattern,in which only one threshold is tr
154、ained or learned.In this case,the rate switching setup time is short(generally within 1 ms),which is negligible for the main device.In addition,high switching reliability is ensured.The switching setup time is closely related to the code pattern corresponding to the target rate.When the target rate
155、is 50 Gb/s and the PAM4 code pattern is used,the CDR or DSP chip needs to train or learn three thresholds.As a result,the switching setup time may be several or even dozens of seconds,and the switching may fail.In this case,the optical module must proactively report the maximum switching setup time
156、and switching success flag.With the switching success flag,the main device obtains the switching state of the optical module(distinguishing between the egress and ingress channels),after which negotiations at the CPRI or eCPRI layer can be performed.4.Reporting of transmission latency For optical mo
157、dules,optical-to-electrical conversion introduces transmission latency,which is related to factors such as the electrical chip scheme,modulation format,and PCB cabling.For 10G and 25G optical modules,such latency is usually hundreds of picoseconds,which has little impact on fronthaul links.However,t
158、he transmission latency introduced by DSP-based 50G optical modules is up to dozens of nanoseconds,which may affect the fronthaul synchronous transmission system.Therefore,a register must be defined in the management interface to claim the transmission latency introduced by the optical module,assist
159、ing the main device in analysis.5.Reporting of support for new functions Compared with CDR-based modules,DSP-based 50G optical modules provide new functions such as loopback,SNR detection,and BER detection.The supported new features and functions can be described in the optical module management int
160、erface.In addition,the management interface provides registers,through which the detection results can be obtained.White Paper on Survey of Optical Modules in Wireless Fronthaul 18 To address the preceding issues,a new management interface should be defined for next-generation 5G fronthaul optical m
161、odules.Based on current research,considering the software switching cost and hardware cost of fronthaul optical modules,SFF-8472 is reused and registers are defined for new features to reduce related costs.For details about the MFH50 encapsulation protocol,see MFH50 management interface V0.1.3.4 MFH
162、50 Test Standards The test methods of optical transceiver modules for optical communication have been released in the industry,involving two parts:YD/T 2798.1-2015 Optical transceiver module for optical communication test methods-Part 1:Single-wavelength type and YD/T 2798.2-2020 Optical transceiver
163、 module for optical communication test methods-Part 2:Multi-wavelength type.In wireless fronthaul scenarios,the test methods will be optimized with reference to MFH50,considering special requirements for dispersion,MPI and the efficiency and accuracy of TDECQ and PAM4 eye pattern tests.3.4.1 Eye Pat
164、tern Test The eye mask margin commonly used for NRZ signals is not applicable to PAM4.Instead,a new parameter TDECQ is added to represent the performance of PAM4 transmitters,and TDECQ,short for Transmitter Dispersion Eye Closure Quaternary,is the main indicator used to evaluate the communication qu
165、ality.Figure 12 shows the IEEE TDECQ test networking.The networking has strict requirements on the polarization state,dispersion,insertion loss,and return loss of the tested optical link,and uses the short stress pattern random quaternary(SSPRQ)as the test pattern.In strict standard tests,optical li
166、nks need to be set up according to the TDECQ test networking,and due to the difficulty in constructing complex test networks in the manufacturing and engineering environments,it is good practice to optimize the test methods based on the requirements in the manufacturing,verification,and engineering
167、acceptance phases.Figure 12 TDECQ test networking(source:IEEE Std 802.3cdTM-2018)3.4.2 Rate Switching Setup Time The rate switching setup time refers to the time required for an optical module to switch between rates.In the era of 25G optical modules,the setup time for rate switching from 25G to 10G
168、 is generally at the millisecond scale.However,in the era of 50G optical modules,the setup time is expected to be several seconds or even dozens of seconds.This is because PAM4 encoding is used,three decision thresholds are set,and chip adaptive equalization takes a certain period of time.Therefore,
169、the rate switching setup time of optical modules must be acknowledged during rate negotiation between wireless devices.White Paper on Survey of Optical Modules in Wireless Fronthaul 19 Figure 13 NRZ and PAM4 eye patterns Definition of setup time:Electrical-optical channel setup time:The time starts
170、when the I2C issues a rate switching command to the optical module and ends when the modules optical port(point A2)outputs the corresponding optical signal and reports the flag bit over the I2C interface,to indicate that the optical module is locked and working normally.The setup time assumes that t
171、he signals at the electrical port(point A1)meet signal quality of the target rate.Optical-electrical channel setup time:The time starts when the I2C issues a rate switching command to the optical module and ends when the modules electrical port(point B2)outputs the corresponding electrical signal an
172、d reports the flag bit over the I2C interface,to indicate that the optical module is locked and working normally.The setup time assumes that the signals at the optical port(point B1)meet signal quality of the target rate.Figure 14 Logical diagram of the rate switching setup time test White Paper on
173、Survey of Optical Modules in Wireless Fronthaul 20 Figure 15 Rate switching setup time test 3.4.3 Latency Test Generally,25G SFP optical modules run on the CDR solution,which ensures very short latency for the optical modules.Such latency is negligible for the fronthaul link.50G optical modules use
174、either of two technical solutions(CDR and oDSP).When the oDSP solution is used,high transmission latency is introduced because the optical module is equipped with the analog-to-digital converter(ADC),DSP,and digital-to-analog converter(DAC).The system design must be compatible with the two hardware
175、solutions.Development for 50G optical modules must set transmission latency thresholds and related test methods.Figure 16 Latency test 3.4.4 Multi-Vendor Test Through decoupling of optical modules from main devices and unified test standards,it is expected that optical modules can be tested independ
176、ently,shortening the time to market(TTM),reducing costs,and improving quality of optical modules.To achieve this,equipment vendors,operators,and optical module suppliers must reach an agreement on the optical module test standards.White Paper on Survey of Optical Modules in Wireless Fronthaul 21 Fig
177、ure 17 Decoupling of the optical module test from the main device test Figure 18 Advantages of test decoupling White Paper on Survey of Optical Modules in Wireless Fronthaul 22 4 Summary and Prospect of Wireless Next-Generation Fronthaul Optical Modules To sum up,the next-generation optical modules
178、for wireless fronthaul will need to cover DRAN and CRAN scenarios as well as live-network standards and wireless device requirements,while achieving optical fiber saving,low power consumption,and high cost-effectiveness.To achieve this,it is recommended that the next-generation optical modules for w
179、ireless fronthaul comply with the following key specifications:Ambient temperature:Optical modules must be able to tolerate a wide range of climatic conditions,and can work properly in temperatures of 40C to+85C(industrial grade)or 20C to+85C(extended commercial grade).Power consumption of optical m
180、odules:It is recommended that the power consumption of 50G gray optics and WDM optical modules be under or equal to 2 W.Link budget:It is recommended that the link budget of 50G optical modules be not less than that of 25G optical modules.Link performance of optical modules:Optical modules must offe
181、r MPI detection and MPI compensation features(specifications to be determined).Dispersion must meet the transmission requirements of CWDM modules that have wavelength of 1371 nm and a transmission distance of 10 km.Multi-rate negotiation:The rate of a fronthaul optical module must match the specific
182、ations of wireless main devices.It is recommended that 50G optical modules support rate reduction.Encapsulation protocol:All of existing wireless fronthaul optical modules(with a rate of 25G,10G,and lower)comply with SFF-8472.It is recommended that SFP and SFF-8472 be applied to wireless fronthaul 5
183、0G optical modules.To meet the requirements of intelligent O&M features,it is recommended that certain registers such as those related to SNR,power-on duration,and multi-rate compatibility be defined with reference to SFF-8472 and CMIS.For details,see the 50G optical module standard defined by IPEC
184、MFH50.This white paper will be updated accordingly to include relevant technical research of fronthaul optical modules.With the continuous evolution of wireless fronthaul solutions,IPEC will conduct research on standards of fronthaul optical modules,including those of 100G or higher,which will serve
185、 as a catalyst to drive the field towards 5.5G and 6G.White Paper on Survey of Optical Modules in Wireless Fronthaul 23 5 Reference 1.Next-Generation 5G Bearer Optical Module White Paper 2.IEEE Std 802.3-2022:IEEE Standard for Ethernet 3.ITU-T G.9806(Amend 2)4.YD/T 3713-2020:50Gb/s PAM4 Modulation P
186、luggable Transceiver 5.YD/T 2759.3-2021:Single Fiber Bi-Directional(BIDI)Optical Transceiver Module-Part3:50Gb/s 6.YD/T 3131-2016:SFP/SFP+optical transceiver module between BBU and RRU for base station interconnecting.7.YD/T 3125.2-2019:Enhanced SFP transceiver(SFP+)used in communication.Part 2:25 G
187、bit/s.8.YD/T 2759.2-2020:Single fiber bidirectional optical transceiver module Part 2:25Gb/s.9.YD/T 4019.1-2022:25Gb/s wavelength division multiplexing(WDM)optical transceiver module Part 1:CWDM.10.YD/T 4019.2-2022:25Gb/s wavelength division multiplexing(WDM)optical transceiver module Part 2:LWDM 11
188、.YD/T 4019.3-2022:25Gb/s wavelength division multiplexing(WDM)optical transceiver module Part 3:DWDM 12.YD/T 4019.4-2022:25Gb/s wavelength division multiplexing(WDM)optical transceiver module Part 4:MWDM 13.Mobile Optical Pluggables Alliance(MOPA):Technical paper Version 2.1 White Paper on Survey of Optical Modules in Wireless Fronthaul 24