Sycamore Networks, Inc.

Mehrdad Givehchi

An optical receiver circuit includes a differential limiter amplifier receiving a binary electrical waveform generated by an optical-to-electrical converter receiving an optical communications signal. Low-pass filter circuits are coupled to differential outputs of the limiter amplifier to obtain the average DC values of the mirror-image output signals. The outputs of the low-pass filter circuits are provided to a differential amplifier to obtain the difference between these average DC values. The output of the differential amplifier is provided to an integrator circuit whose slowly-varying output is provided to the limiter amplifier to establish a switching threshold for distinguishing logic &ldquo;0&rdquo;s from logic &ldquo;1&rdquo;s in the received data signal. The switching threshold is automatically adjusted in response to varying operation conditions such as changes in the received optical signal power. Set point adjustment circuitry provides a variable set point input to the integrator circuit to minimize the effects of noise in the received optical signal. The receiver circuit can be used with error-detection circuitry and performance monitoring circuitry to characterize the sensitivity of error performance to the value of the switching threshold. This sensitivity information can be used to adjust transmit signal powers to achieve a desired balance of optical signal to noise ratios among a number of channels in a WDM signal.

Growing community of inventors

Boston, MA, United States of America

Mehrdad Givehchi