What Is A 100g Optical Transceivers?

100G optical transceiver refers to an optical transceiver with transmission rate of 100Gbps, with 4 channels for transmitting and receiving optical signals, each of them is 25G. And the commonly used packaging is QSFP28.

Fiber Optic Transceiver Module

Classification Of Optical Transceivers

There are 5 main types divided by IEEE and MSA organizations: 100G QSFP28 SR4 / 100G QSFP28 CWDM4 / 100G QSFP28 PSM4 / 100G QSFP28 LR4 / 100G QSFP28 ER4.

Type	Interface	Mode	Wavelength	Distance
100G QSFP28 SR4	MPO	MM	850nm	100M
100G QSFP28 CWDM4	LC duplex	SM	1271-1331nm	2KM
100G QSFP28 PSM4	MPO	SM	1310nm	2KM
100G QSFP28 LR4	LC duplex	SM	1295.56-1309.14nm	10KM
1OOG QSFP28 ER4	LC duplex	SM	1295.56-1309.14nm	40KM

Comparison of 100G Optical Transceivers

100G SR4 is more and more popular in the data center after the rate of single-channel chip reached 25G as well 100G SR10 was gradually replaced by 100G SR4.

However, the longest transmission distance of 100G SR4 is up to 100M, which is not enough in data center. Then100G QSFP28 CWDM4 and PSM4 come out.

100G QSFP28 LR4 can reach 10km and the cost has dropped with product upgrades. Therefore there is hardly advantage of 100G QSFP28 CWDM4 and 100G QSFP28 PSM4.

①、100G QSFP28 CWDM4 VS 100G QSFP28 PSM4

The transmission distance of 100G CWDM4 and 100G PSM4 can both reach 2km and be used in data center. But different in solutions.

There are four wavelengths for 100G CWDM4: 1271/1291/1311/1331with 20nm interval. It modulated by DML (Direct Modulated Laser) at the same time transmit and receive by two single-mode optical fibers. There is only one wavelength for 100G PSM4 which is 1310nm. It has four integrated modulators and one laser, connected an 8-core MPO fiber—4 transmitters and 4 receivers.

There cost of CWDM4 and PSM4 transceivers are comparable but MPO fibers are more expensive than LC fibers. Therefore the overall cost of PSM4 is higher CWDM4 when apply to long distance.

②、100G QSFP28 CWDM4 VS 100G QSFP28 LR4

LR4 and CWDM4 both use MUX and DEMUX to deal with signals. The wavelength interval of CWDM4 is 20nm while LR4 is 4.5nm. LR4 uses EML (Electro-absorption Modulated Laser) incluing DML and EAM modulator used in CWDM4, the transmission distance is up to 10km. Therefore the cost of LR4 is higher than CWDM4.