Spread-spectrum bias control

摘要

An optical modulator has a continuous wave laser input, an RF input, a bias and dither input and an output. A photodiode connected to an output tap produces a voltage that is amplified. Noise is removed from the amplified output. A spread-spectrum dither harmonic is generated and supplied to a multiplier with the amplified and filtered feedback and is used to create a DC bias. A spread-spectrum dither is created and added to the DC bias. Spread spectrum dither and bias both are applied to the bias input of optical modulator. The bias and spread spectrum dither controller is usable with other non-optical modulators and other electronic devices.

主权项

1. A system comprising:
a modulator, a RF signal source connected to the modulator, a signal output connected to the modulator, a tap connected to the signal output of the modulator, a dither and bias controller connected to the modulator and to the tap,the dither and bias controller having:
a controller input connected to the tap, and a controller output connected to the modulator, the controller having a receiver connected to the tap for providing a bias, a summing circuit having a bias input, a spread-spectrum dither source connected to the summing circuit, the summing circuit having a bias and spread-spectrum dither output connected to the controller output, further comprising a band pass filter connected to an output of the receiver and a multiplier circuit connected to the band pass filter, a frequency source connected to the multiplier circuit, a time integrator and error amplifier or power detector connected between the multiplier circuit and the summing circuit for producing the bias, wherein the frequency source is a local oscillator, the spread-spectrum dither signal source produces a pseudo-random phase modulated continuous wave sinusoidal dither signal, and the local oscillator produces a continuous wave sinusoidal signal that is phase locked to the continuous wave sinusoidal dither signal.