The QSFP28 CWDM4 and QSFP 100G PSM4 both can be transmitted on four wavelengths. But the QSFP28 PSM4 uses four independent wavelengths to transmit signals via 8-fiber MTP/MPO single mode fiber patch cables. While the QSFP 100G CWDM4 enables four wavelengths to be multiplexed to transmit on a single fiber, so the transmission can be achieved by just 2-fibers LC duplex single mode fiber patch cables.

by *** on 12/02/2021

CWDM can provide larger transmission capacity, saving optical fiber resources(signals of different rates and formats can be mixed, as long as the rates at both ends of the combined wave front and the split wave rear are consistent)

by *** on 12/02/2021

The main difference is the Forward Error Correction (FEC) function. For QSFP 100G CWDM4, it is required for supporting FEC. As for the 100G CLR4, the FEC is an optional function. It can support operation with and without FEC. The 100G CLR4 can enable FEC function for increasing link margin or maintain the performance of low latency and low power without FEC function.

by *** on 12/01/2021

The main difference between 100GBASE-CWDM4 QSFP28 and 100GBASE-LR4 QSFP28 is the working wavelengths. For 100GBASE-CWDM4 QSFP28, the operating wavelength of is 1271nm, 1291nm, 1311nm, 1331nm, wavelength interval is 20nm; and for 100GBASE-LR4 QSFP28, the operating wavelength is 1295.56nm, 1300.05nm, 1304.58nm, 1309.14nm, and the wavelength interval is about 5nm. So they can not communicate with each other.

by *** on 05/20/2020

FEC (Forward Error Correction) is an error correction technique to detect and correct a limited number of errors in transmitted data without the need for retransmission. It works by adding redundant bits to a bitstream to help the decoder detect and correct some transmission errors without the need for retransmission. This function needs to be turned on by the transmission device.

by *** on 05/10/2020