How to Choose 100G Optical Transceiver Module

Feb 12, 2025

With the rapid development of data center, for the application of 100G medium and long-distance, 100G CWDM4 and 100G PSM4 have been launched in the case of short transmission distance of 100G SR4.

1. 100G CWDM4 and 100G LR4
Both 100G LR4 and 100G CWDM4 optical transceiver module multiplex 4 parallel 25G channels into one 100G optical fiber link via optical components MUX and DEMUX. The difference between them is that LR4 module is made with LAN-WDM technology, while CWDM4 with CWDM technology.
In addition, the transmission distance of 100G LR4 optical module is 10km, while the 100G CWDM4 2km maximum. Compared with the 100G LR4 optical transceiver module, the 100G CWDM4 optical transceiver module has much lower price, and it can meet the needs of medium and long-distance transmission in data center. At the same time, in the scenario of transmission distance of 2km and below, the cost of CWDM4 solution is more cost-effective.
In summary, the 100G CWDM4 standard well supplements the gap caused by the high cost of 100G LR4 within 2Km.

2. 100G CWDM4 and 100G PSM4
Both 100G CWDM4 and 100G PSM4 transceivers are developed in the same period of communication technology, but they have many differences in speed, wavelength, cost and application scenarios.
The transmission distance of 100G CWDM4 and 100G PSM4 both can reach 2km, and both can be used for medium-distance transmission in data centers.
100G CWDM4 has 4 wavelengths: 1270/1290/1310/1330, and the interval of each wavelength is 20nm. DML (Direct Modulated Laser) is used to directly modulate the injection current of the laser to realize signal modulation. At the same time, CWDM4 uses 2 single-mode optical fibers to complete signal transmission and reception. The 100G PSM4 has a wavelength of 1310nm, uses 4 integrated silicon photonic modulators and a distributed feedback laser, and uses an 8-core MPO cable, 4 transmit and 4 receive, to complete signal transmission and reception at a single-channel 25G rate.
In terms of cost, since MPO cables are much more expensive than LC cables and use wavelength division multiplexers, the cost of PSM4 optical modules is higher than that of CWDM4 optical modules. CWDM4 only needs two single-mode optical fibers for bidirectional transmission and reception, which is far less than the 8 single-mode optical fibers of PSM4. As the distance increases, the total cost of the PSM4 solution rises very quickly.

From the above, we can see that the characteristics and applications of LR4, CWDM4 and PSM4 are different, so when choosing, we should evaluate and decide based on actual needs and Internet distance design. If a longer transmission distance or multimode fiber option is required, CWDM4 is more suitable. For short-distance transmission or high-power consumption requirements, PSM4 is a better choice.

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