Power equalization-based disaggregated optical network using switched gain equalization controlled amplifiers

Optical network disaggregation is an attractive agreement to avoid vendor lock-in in choosing desirable partners based on lead time of delivery and facilitates strong negotiations. Disaggregation of conventional coherent transceivers (XCVRs) with 400G ZR+ technologies (of similar bandwidth density and form factor QSFP-DD) allows operators to enjoy significant cost reduction and substantial power savings in high-capacity IP over a WDM transmission. However, interoperability between low power and high back-to-back required optical signal-to-noise ratio (OSNR) of ZR+ and high power with relatively lower back-to-back required OSNR of conventional coherent XCVRs limits the performance of the latter, which makes disaggregation more complex. This can be avoided by equalizing the power of ZR+ and conventional XCVRs, by wavelength-selective switches (WSSs) in re-configurable optical add/drop multiplexers. However, such power equalization can lead to lower link OSNR, originating from insertion loss and penalty caused by cascaded WSSs. In this Letter, we use a dynamic gain equalizer of a switched gain equalization controlled (SGEC) amplifier at each in-line amplifier site to equalize the powers, without introducing insertion loss or filter penalty. We report a field trial of a low power 400G-ZR+ QSFP-DD-DCO as an alien channel over ten high-power coherent host channels, interoperating with open forward error correction, between two different vendors. We obtain a similar Q-margin in the absence and presence of 400-ZR+ channel, suggesting the equalization by SGEC amplifiers. We further simulate the power and OSNR evolution of channels along the field trial link to verify the equalization. Simulation results are consistent with that of the field trial.