Optical dispersion imposed on a communications signal conveyed through an optical communications system is compensated by modulating the communications signal in the electrical domain. A compensation function is determined that substantially mitigates the chromatic dispersion. The communications signal is then modulated in the electrical domain using the compensation function. In preferred embodiments, compensation is implemented in the transmitter, using a look-up-table and digital-to-analog converter to generate an electrical predistorted signal. The electrical predistorted signal is then used to modulate an optical source to generate a corresponding predistorted optical signal for transmission through the optical communications system.

Optical dispersion compensation in the electrical domain in an optical communications system

Optical techniques, devices and systems for combining duobinary modulation and optical subcarrier multiplexing in optical communication applications. An analog mixer is used to mix a duobinary signal for a data channel and a local oscillator signal to produce a modulation control signal for controlling the subsequent optical subcarrier multiplexing modulation. Various optical subcarrier multiplexing modulation techniques may be used including optical single sideband modulators and optical double sideband modulators.

Optical communication using duobinary modulation

High speed optical modulators can be made of k modulators connected in series disposed on one of a variety of semiconductor substrates. An electrical signal propagating in a microwave transmission line is tapped off of the transmission line at regular intervals and is amplified by k distributed amplifiers. Each of the outputs of the k distributed amplifiers is connected to a respective one of the k modulators. Distributed amplifier modulators can have much higher modulating speeds than a comparable lumped element modulator, due to the lower capacitance of each of the k modulators. Distributed amplifier modulators can have much higher modulating speeds than a comparable traveling wave modulator, due to the impedance matching provided by the distributed amplifiers.

Distributed amplifier optical modulators

The present invention includes novel techniques, apparatus, and systems for optical WDM communications. Tunable lasers are employed to generate subcarrier frequencies representing subchannels of an ITU channel to which client signals can be mapped. Client circuits can be divided and combined before being mapped, independent of one another, to individual subchannels within and across ITU channels. Subchannels may be independently routed to a single subchannel receiver filter, such that each subchannel detected at the receiver may come from a different source location. Network architectures and subchannel transponders, muxponders and crossponders are disclosed, and techniques are employed (at the subchannel level/layer), to facilitate the desired optical routing, switching, concatenation and protection of client circuits mapped to these subchannels across the nodes of a WDM network. Subchannel hopping may also be used to increase the optical network security.

Optical subchannel routing, protection switching and security

The method and system are disclosed for automatic feedback control of integrated optical quadrature modulator for generation of optical quaternary phase-shift-keyed signal in coherent optical communications. The method comprises the steps of detecting at least a part of an output optical signal from the QPSK modulator, extracting of a particular portion of the output signal in frequency domain, and processing the signal in frequency domain to optimize the transmission of an optical link. The system and method of optical communications in fiber or free space are disclosed that implement the quadrature data modulator with automatic feedback control.

Quadrature modulator with feedback control and optical communications system using the same

An optically implemented wide bandwidth correlation system ( 10 ) that employs a multi-mode imaging device ( 42 ) and a particular modulation format to provide both in-phase and quadrature phase correlation components in a single correlation process. The correlation system ( 10 ) includes an optical source ( 12 ) that generates a laser beam ( 14 ) that is split into a first beam path ( 18 ) and a second beam path ( 20 ). The first split beam and a first electrical signal are applied to a first modulator ( 22 ) in the first path ( 18 ) and the second split beam and the second electrical signal are applied to a second modulator ( 24 ) in the second path ( 20 ). The modulated beams are then applied to the optical imaging device ( 42 ) that causes the beams to interfere with each other within an optical cavity ( 48 ). Four optical outputs are connected to the optical cavity ( 48 ) at strategic locations to provide a zero phase output and a π phase output that represent the in-phase correlation component, and a π/2 quadrature phase output and a 3π/2 quadrature phase output that represent the quadrature phase correlation component. A photodetector (60-66) detects each of the output signals from the imaging device ( 42 ) to provide electrical signals indicative of the phase outputs. A first differential amplifier ( 68 ) receives the electrical signals of the in-phase component and a second differential amplifier ( 70 ) receives the electrical signals of the quadrature phase component. The differential amplifier outputs are applied to separate integrators ( 72,74 ) to sum the signals for the correlation process. The modulators can be Mach-Zehnder interferometer modulators to provide a single sideband suppressed carrier modulation so that the in-phase and quadrature phase correlation components can be simultaneously generated.

Optically implemented wideband complex correlator using a multi-mode imaging device

An integrated optoelectronic device (1) includes a substrate(4), at least one optoelectronic component (2) provided on the substrate (4), and a waveguide (9a ... 9n) provided on the substrate (4) and optically connected to the at least one optoelectronic component (2). The waveguide (9a ...9n) is made of a sol-gel glass. A method for making the integrated optoelectronic device (1) includes the steps of providing a substrate (4), providing at least one optoelectronic component (2) on the substrate (4), and providing at least one sol-gel glass waveguide (9a ... 9n) on the substrate (4) and optically connected to the at least one optoelectronic component (2).

Integrated optoelectronic device and method for making same

An optical switching device that routes an optical data packet using an all optical architecture signal detection and switching system. The packet includes header bits, data bits and a reset bit. The header bits identify the switch state for routing the data packet and the specific routing information for distinct portions of the data packet. The header bits are transmitted at an optical carrier frequency different than the carrier frequency of the data bits. The reset bit resets the switch element processor to enable it to process and route the next data packet. The frequency of a particular header bit affects the index of refraction of a Bragg grating of a detector and the output of the detector is provided to a switch that determines the routing path of the packet. A return command resets the diffraction grating so that it does not affect subsequent header bits.

All optical switching routing system

In this work, multimode interference in a semiconductor optical amplifier is used to simultaneously split (× 10) and amplify a RF signal on an optical carrier.

Analog Signal Splitting and Amplification for Optically-Controlled Phased-Array Antennas

An integrated optoelectronic device (I) includes a substrate(4), at least one optoelectronic component (2) provided on the substrate (4), and a waveguide (9a ... 9n) provided on the substrate (4) and optically connected to the at least one optoelectronic component (2). The waveguide (9a...9n) is made of a sol-gel glass. A method for making the integrated optoelectronic device (1) includes the steps of providing a substrate (4), providing at least one optoelectronic component (2) on the substrate (4), and providing at least one sol-gel glass waveguide (9a ... 9n) on the substrate (4) and optically connected to the at least one optoelectronic component (2).

James E. Leight

Papers

Optically implemented wideband complex correlator using a multi-mode imaging device

Integrated optoelectronic device and method for making same

All optical switching routing system

Analog Signal Splitting and Amplification for Optically-Controlled Phased-Array Antennas

Method for making an integrated optoelectronic device