An ultra-fast electrooptic analog-to-digital converter is described. The A/D converter includes an electrooptic modulator that generates a modulated light beam from an incident light beam in response to an applied modulation signal. An optical demultiplexer is positioned to receive the modulated light beam. The optical input of a respective one of a plurality of photodetectors is optically coupled to a respective one of a plurality of demultiplexed modulated light beams. Each of the plurality of photodetectors generates an electrical signal in response to an intensity of the demultiplexed modulated light beam that is coupled to its optical input. A plurality of charge comparators compares electrical signals generated in response to the intensities of the demultiplexed modulated light beam to a reference signal. The output of each of the plurality of charge comparators generates a digital representation of the incident light beam.

Optically sampling, demultiplexing, and A/D converting system with improved speed

A linearized optical sampler is described. The optical sampler includes an electro-optic modulator having an optical signal input, an electrical signal input, and at least two optical signal outputs that generate at least two modulated optical signals. The optical sampler also includes at least two detectors each of which being optically coupled to a respective one of the at least two modulated optical signals. Each detector generates an electrical signal in response to an optical intensity of the respective one of the at least two modulated optical signals. The optical sampler also includes a signal processor electrically connected to each of the at least two detectors. The signal processor applies an inverse transform of the modulator transfer function. The signal processor also generates an electrical signal from the electrical signals generated by the detectors and from the inverse transform that is linearly related to an RF signal electrically that is coupled to the electrical signal input.

Linearized optical sampler

: The objective of this program was to conduct exploratory development of a 1 Gbps single-pass single-unit (unmultiplexed) modulator for use with a mode-locked and frequency-doubled neodymium YAG laser in a space laser communication system. The exploratory effort was directed toward the investigation and solution of problems for Pulse Gated Binary Modulation (PGBM) modulator operation. The modulator was to operate at data rates up to 1 Gbps and be able to handle 0.53 micrometer laser power up to 0.25 watts while maintaining its specified operating characteristics. The performance goals were (1) a static extinction ratio of 100 to 1 or greater, (2) a worst case dynamic extinction ratio of 30 to 1 or greater with a 1 Gbps pseudorandom code input, and (3) a static optical transmission of at least 80%. This effort was to develop the Gbps 0.53 micrometer modulator and provide a driver in breadboard form to be used as a laboratory tool to demonstrate the feasibility of the 1 Gbps modulator design concept. Several breadboard modulator-driver combinations were fabricated and evaluated. No hardware delivery was required. The four modulator units developed and evaluated under this program used the baseband and digital Pulse Gated Binary Modulation (PGBM) format.

L. B. Allen

Papers

Advanced Modulator II