US 11,381,444 B2 · Method and apparatus for coherent transmitter calibration

Abstract

Methods and apparatus for coherent transmitter calibration are provided that employ direct detection (DD) using one single photodetector (PD). The provided method and apparatus do not require hardware for coherent reception, or additional ADCs for quality control. An additional optical tone is added to a QAM optical signal that is outside the band of the QAM optical signal. The result of this is that after direct detection, there is a correlation between the real and imaginary parts, and the imaginary part can be recovered with a Hilbert transform. The estimated QAM optical signal obtained by direct detection is used to perform a transmitter factory calibration method to calibrate for one or more transmitter impairments and/or to perform in-line self-calibration.

Claims20

Dependent claims

A method of calibrating a coherent transmitter, the method comprising:

optically coupling an optical frequency tone to a coherent QAM optical signal, the tone having a carrier frequency outside a bandwidth of the coherent QAM optical signal to produce a coherent QAM optical signal with added optical frequency tone, such that there is a gap between the bandwidth of the coherent QAM optical signal and the frequency of the optical frequency tone;
performing photodetection on the coherent QAM optical signal with added optical frequency tone with a single photodetector to produce a photodetector output containing a DC term, a signal beat term, and a signal-signal beat interference (SSBI) term;
calibrating the transmitter based on the photodetector output.

Dependencies are inferred from the claim text.

Method and apparatus for coherent transmitter calibration

Life of this patent

Method and apparatus for coherent transmitter calibration

Life of this patent

Abstract

Claims20