Methods to increase the transmission rate of an optical module

As data centers and telecom carriers have higher requirements on optical transceiver transmission rates, what technologies do optical transceiver manufacturers use to achieve higher transmission rates? This article will reveal the answer.

1. Increase the baud rate. Baud rate is the modulation rate of the data signal to the carrier. This method is mostly used for low-rate optical modules, such as 10G.

2. Use multi-channel parallel transmission technology, which adopts four channels of the same wavelength for transmission. The main working wavelengths are 850 and 1310nm, and the main representative optical modules are 40G and 100G SR4/PSM4.

3, the use of WDM technology to improve the transmission rate

(1) LAN WDM thin wavelength division multiplexing, it is located in the O-band (1260nm ~ 1360nm) range of 1269nm to 1332nm band 12 wavelengths, wavelength interval is 4nm. The optical modules using this technology are 100G LR4/ER4/ZR4, and their operating wavelengths are 1295, 1300, 1304, and 1309.nm.

(2) CWDM coarse wavelength division multiplexing technology, representing optical modules such as 100G CWDM4 and 100G CLR4.

(3) SWDM short wavelength division multiplexing technology, the wavelength range is between 850-950nm, the band interval is 30nm, respectively 850, 880, 910, 940nm, representing the optical module has multi-mode 40G SWDM4, 100G SWDM4.

4. Using pulse amplitude modulation (PAM4) to carry 4 times the amount of data in the same time period instead of non-return to zero modulation (NRZ) to achieve higher data rate. Whether you use NRZ or PAM4, you need some sort of forward error correction (FEC) algorithm. Because the interference signal has a strong effect on PAM4, a more complex FEC algorithm is required. The representative optical modules are 50G SFP56 SR, 200G QSFP56 FR4 (4*53Gb/s PAM4), 400G QSFP-DD SR8 (8*53Gb/s PAM4).