Abstract: Methods and apparatus for stabilizing or otherwise controlling optical signal power levels in a multi-channel optical communication system. A multi-channel optical signal is detected in a single receiver, and the resulting detected signal is supplied to a correlator. The correlator correlates the detected multi-channel signal with a data signal associated with a particular channel to be controlled in order to generate a measure of the optical signal power of the particular channel. The measure is utilized in a feedback control loop to control an optical signal power level of the particular channel. The correlator may generate the measure of optical signal power by mixing the detected signal and the data signal in an RF mixer, by multiplying the detected signal and a data signal in the form of a unique identifier associated with the particular channel, or by using other suitable correlation techniques.

Abstract: A Wavelength Division Multiplexing (WDM) optical monitor, based on concatenated fiber gratings, uses a single modulator and detector and has high dynamic range and good sensitivity through signal averaging. The WDM optical monitor may be implemented in a time-domain or frequency-domain embodiment and used for SNR measurement of WDM optical signals.

Abstract: A system and method for maintaining alignment between a source and router in a Wavelength Division Multiplexed (WDM) fiber optic network. In a preferred embodiment, a narrow band of the wavelengths emitted by the WDM source is designated as a monitor channel. The monitor channel is matched in wavelength to a fiber grating that is located in the optical path between the source and router so that the grating reflects the monitor channel light while allowing all other source light to pass through unimpeded. By monitoring the reflected light and adjusting the source wavelengths to maximize the amount of reflected light, alignment between the source and router is maintained.

Abstract: The specification describes lightwave systems with remotely powered photoelectric generators. Optical power transmitted through the fiber is incident on a remotely located photodiode array. High power conversion efficiency coupled with a specially designed diode array generates sufficient power to operate electromechanical or electrooptic apparatus in the remote station. Long wavelength photodiodes are serially connected to increase the voltage to practical operating levels. In a communication system, with an optical signal transmitted with the optical power, multiplexers are used for separating the optical power from the optical signal.

Abstract: In a fiber optic communication system, a multifrequency light source generates a signal having a plurality of discrete and temporally spaced wavelengths. The wavelengths can be modulated with data for transmission in an optic medium. The multifrequency light source is cascaded with a power splitter for dividing the generated signal into a plurality of multifrequency signals of substantially equal power. The wavelengths in the plurality of signals may be modulated with data for transmission in an optic medium to a plurality of optic receivers for retrieval of the data.

Abstract: An Add/Drop circuit for use in optical wavelength-division multiplexed systems includes fiber coupled four-port polarized beamsplitters and fiber Bragg grating filters.

Abstract: A correlation feedback method and apparatus for multi-channel stabilization of a multi-channel transmitter in which a single external receiver is used to detect the total power output from the multi-channel transmitter and to control each channel by correlating the total power output signal with channel data to measure the channels' signal power and control the output power via a feedback loop. The inventive system is suitable for use with and able to accommodate both integrated lasers and an array of discrete independent lasers; the system is also equally applicable for use with channels comprising random independent data or broadcast data.

Abstract: Stability of a pump laser for activating an erbium amplifier is enhanced by a grating which results in laser operation in the coherence collapse regime.

Abstract: The specification describes lightwave systems with remotely powered photoelectric generators. Optical power transmitted through the fiber is incident on a remotely located photodiode array. High power conversion efficiency coupled with a specially designed diode array generates sufficient power to operate electromechanical or electrooptic apparatus in the remote station. Long wavelength photodiodes are serially connected to increase the voltage to practical operating levels. In a communication system, with an optical signal transmitted with the optical power, multiplexers are used for separating the optical power from the optical signal. Also disclosed are optimally designed photodetector arrays in which the photodetector elements are segments of a circular or polygonal circularly symmetric array to increase the fill factor of the array.