Development status of 5G optical module
At present, the module types and interface characteristics of optical module solutions in various scenarios are different and complex. Domestic and international standardization organizations ITU-T, Institute of Electrical and Electronics Engineers (IEEE), Optical Internet Forum (OIF), 4WDM and other multi-source agreements (MSA), China Communications Standards Association (CCSA) are continuing to promote Standardization process for each type of module. The 5G bearer working group of the IMT-2020 (5G) promotion group has organized two evaluations of multi-vendor and multi-type 5G optical modules to further promote the development level of 5G optical modules.
The 25G pre-growth gray light module is gradually matured, and the color light module presents WDM program competition.
The front-end gray light module can be realized by two laser chips of 25G baud rate or 10G baud rate. The reliability requirements and mass production process requirements of 25G baud rate industrial grade laser chips are high, and the market supply channels are limited. The 10G baud rate industrial grade laser chip can make full use of the mature supply chain, which can effectively reduce the cost of the optical module. At present, the industry mainly has two implementation schemes of overclocking and PAM4 high-order modulation. In addition, IEEE 802.3cc has completed the 25GbE single-mode fiber interface specification. CCSA has also released the domestic industry standard YD/T 3125.2-2019 for 25Gbit/s dual-fiber two-way gray light module. The domestic industry standard for 25Gbit/s BIDI gray light module is expected. Completed this year.
For the pre-pass color light module, considering the factors of dispersion and cost, CWDM, LWDM, MWDM, DWDM and other competitive solutions appear, mainly occupying C-band and O-band. From the perspective of the wavelength adjustment mode of the module, it is mainly divided into 25Gbit/s fixed wavelength color light module and 25Gbit/s tunable optical module. At this stage, there are two implementations for fixed-wavelength applications. One is to choose a 6-wave mode for construction (6 waves in CWDM or 4 waves in LWDM + 2 waves in CWDM). Another way is to consider 5G and previous-generation communication compatibility and high-bandwidth application scenarios, choose to build in 12-wave or more wavelengths (MWDM/LWDM/DWDM), in which part of the wavelengths in CWDM and MWDM can share the 100G CWDM4 industry chain. The laser uses DML scheme; LWDM can be based on 100G CWDM4, 100G LR4, 400G LR8 and other industrial chains. Some lasers still need to use EML scheme, but EML price is not competitive in the pre-transmission scenario, and the subsequent evolution needs to be DML scheme.
In some scenarios, the 25Gbit/s tunable optical module will replace the 25Gbit/s fixed-wavelength color light module because of its networking and maintenance convenience. However, its integration and power consumption requirements are high, and domestic suppliers are speeding up research and development. Progress is expected to achieve industrialization by 2020. The ITU-T G.698.4 standard (G.Metro), which was drafted and released by China, has defined 10Gbit/s access type WDM networking and wavelength-independent, colorless implementation mechanism. Currently ITU-T is in the G.698.x series of standards. (G.698.1, G.698.2, G.698.4) also initiated revisions for 25G DWDM interface applications with a view to unifying the industry chain and further reducing costs.