Adaptive Compensation Circuitry for Suppression of Distortions Generated by the Dispersion-Slope of Optical Components

摘要

A distortion compensation circuit compensates for the distortions generated by the dispersion-slope of an optical component and the frequency chirp of an optical transmitter. The dispersion compensation circuitry can be utilized in the optical transmitter, the optical receiver and/or at some intermediate point in a fiber-optic network. One embodiment of the compensation circuit utilizes a primary electrical signal path that receives at least a portion of the input signal and a delay line; and a secondary signal path in parallel to the primary path that receives at least a portion of the input signal and including: an amplifier with an electrical current gain that is proportional to the dispersion-slope of the optical component, an optional RF attenuator, an optional delay line, a “squarer” circuit, and a “differentiator” circuit. Another embodiment of the disclosure performs simultaneous, and independent, compensation of second-order distortions generated by both the dispersion-slope of a first optical component and the dispersion of a second optical component. Other embodiments of the disclosure perform adaptive predistortion for compensation of distortions generated by the dispersion-slope of a first optical component and the dispersion of a second optical component to maintain optimum compensation even if the dispersion properties of the optical components change with time.

主权项

1. A method, comprising: cancelling substantially composite second order distortion from at least 1) a dispersion-slope of an optical component and 2) frequency chirp of an optical transmitter using a distortion compensation circuit including a parallel combination of an input signal I(t) and a secondary path where a predistortion signal Ipredis(t) is generated according toIpredis=Gopt(I2)twherein copt is a parameter independent of I(t) and is proportional to the dispersion slope Sopt of the optical component according toGopt=(P0SoptSlas)(λ42c2)ηFM2wherein λ denotes the wavelength of the optical signal, c denotes the speed of light in a vacuum, ηFM denotes the laser chirp (also known as the laser FM efficiency) in units of MHz/mA, P0 is the average power output of the laser in mW, Sias denotes the slope of the laser light-current characteristic in units of mW/mA and Sopt denotes the dispersion-slope of the optical component in units of ps/nm2 at wavelength λ.