Our article once discussed that coherent optical communication is the mainstream choice for long-distance transmission in backbone networks and metropolitan area networks. Coherent optical modules include analog coherent ACO and digital coherent DCO. Generally, they are packaged in the CFP series. History of development.
In the beginning, the coherent optical module was packaged in CFP. CFP MSA provides a package width of 82mm and a power consumption of less than 24W, which is enough to put the required three optical components (laser, modulator, ICR) and DSP into the CFP to form a complete coherent transceiver, which is called It is "DCO", which means "digital coherent optics". CFP-DCO can be inserted into any slot designed for CFP, and communicate with digital signals through optical ports. Therefore, a switch or router equipped with a CFP slot can accommodate a short-distance client CFP or a long-distance coherent CFP-DCO transceiver in any slot.
However, low power consumption & small package & large capacity & low cost are the goals that communicators continue to pursue. Therefore, CFP MSA inevitably has to keep up with the size of CFP2. The standard width of CFP2 is 41.5 mm, which initially allowed 12W power consumption. But when DSP technology first started to use, the power consumption and heat were so high that the optical device and the DSP had to be physically separated to prevent the optical device and DSP from overheating. Therefore, a new type of pluggable coherent receiver CFP2-ACO is defined. ACO stands for "Analog Coherent Optics". It moves the DSP outside of the CFP2 and moves it to the circuit board inserted into the CFP2-ACO. The CFP2-ACO communicates with the circuit board by sending analog signals through a special connector.
Both ACO and DCO are designed to integrate the following multiple components:
- Ultra-narrow linewidth laser: The narrower the linewidth, the lower the noise, so it can support QAM high-order modulation.
- Low insertion loss modulator: The minimum loss low insertion loss modulator reduces the need for enhanced erbium-doped fiber amplifier (EDFA) in the module, which can improve the optical signal-to-noise ratio (OSNR) while reducing the size and cost. The stronger, the wider the coverage.
- High sensitivity coherent receiver.
The core difference between the DCO module and the ACO module is that the DCO directly integrates the DSP chip on the optical device, and uses digital communication with the system to solve the problem of inter-vendor exchanges. In addition, because of the higher integration of DCO, the power consumption of DCO is lower than that of ACO module.
However, CFP2-ACO is smaller, and its power consumption is also lower. That is, there are too many analog signal algorithms and they are not compatible with each other. With the development of DSP and optical devices, many manufacturers have developed CFP2 DCO.
As shown in the following table, compared with CFP-DCO, CFP2-DCO performance is significantly improved, whether it is a metropolitan area network or an access network, CFP2-DCO module can meet, and from the perspective of total cost of ownership (TCO), power and density The savings are of considerable value.
Within the power limit of CFP2, CFP2 DCO applications can also be extended to:
- 200G ultra-long-distance transmission: Optical signal-to-noise ratio (OSNR) is less than 14dB, and dispersion compensation technology can achieve transmission over 2000km;
- 400G metropolitan area network transmission: up to 800 or even 1000 kilometers, depending on the quality of the optical fiber link and the span of the EDFA.
Gigalight's 100G CFP DCO and 100G/200G CFP2-DCO optical modules have been commercially available and are specially developed for data center interconnection (DCI) and metropolitan area network applications. In addition, 100G/200G CFP2-DCO in 100G mode can realize communication service intercommunication networking with our first-generation 100G CFP-DCO, further enhancing the stability of equipment and saving replacement costs.
Original link: https://www.gigalight.com/cn/bbs/article-2349.html