Microwave subcarrier and clock recovery by an optically injected CPSO

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Abstract
A technique for recovering phase-locked microwave subcarriers or clocks from optical signals is presented. A coherent phase-locked synchronous oscillator (CPSO) locks to the subcarrier of an optically injected signal and allows coherent demodulation of 1.4-Gb/s PSK modulation of a 4.2-GHz subcarrier. It appears to be a general technique for extracting phase-locked spectral components of optical sources and should prove useful for a variety of modulation schemes. Improved performance is expected from custom oscillators designed for optical injection, which utilize components with enhanced optical sensitivity and allow fiber optic access. The optical wavelength is determined by the Si varactor optical sensitivity and by voltage-controlled oscillator (VCO) availability; other wavelengths (e.g. 1.3-1.5 mu m) should be possible by using VCOs with varactors made of an appropriate material (e.g. InGaAs).