Signal beam

About: Signal beam is a research topic. Over the lifetime, 1881 publications have been published within this topic receiving 20717 citations.

Differential focus blade clearance probe and methods for using same

Abstract: An apparatus and a method for ascertaining a gap between a stationary member and a rotating member are disclosed. At least a reference beam and a signal beam, which have different focal lengths or which diverge/converge at different rates, are fixed to the stationary member and proximate to each other. The beams are projected across a gap between the stationary member and the rotating member toward the rotating member. The reference and signal beams are reflected by the translating member when it intersects the reference and signal beam, and the reflected reference and signal pulses are obtained. One or more features of the reflected reference pulse and the reflected signal pulse, such as a rise time of the pulses, a fall time of the pulses, a width of the pulses and a delay between the reflected reference pulse and the reflected signal pulse, among other factors, are obtained. The width of the gap is obtained using at least one of these factors.

Photometric measuring apparatus

Abstract: A highly stable and sensitive photometric apparatus is obtained by combining a sensitive, stable, unchopped, dual-beam optical photometer with an accurate electronic sensing circuit. The circuit includes PIN silicon diode detectors on which the two beams of the photometer are imaged. One beam is a reference to detect light source variations and the other a signal beam passing through the sample cell of the photometer. The PIN diode outputs are inputs to parametric amplifiers. The amplifier outputs are then provided to log taking means which take the logarithms of the two signals and then take the difference of the two logarithms to provide a final output proportional to absorbtion in the cell.

Wdm optical communication wherein optical beams are modulated by channel discrimination signals of different frequencies by data signals

Abstract: In a wavelength division multiplexed optical communication network which includes a transmitter including a multiplexing arrangement (15-17) for wavelength division multiplexing signal beams of a plurality of channels into the multiplexed signal beam for reception by at least one receiver (12) capable of producing a data carrying intermediate frequency signal by using a local optical beam in receiving the signal beam of a selected channel, the transmitter comprises a modulating arrangement (15) for frequency modulating optical beams of the channels into frequency modulated beams by channel discrimination signals (18) having different frequencies in correspondence to the channels before (19) the signal beams are multiplexed. Besides a receiving arrangement (21-25, 31-32, 35-38) for producing the data carrying intermediate frequency signal and prior to production thereof an information carrying intermediate frequency signal by using the local optical beam in receiving a multiplexed optical beam into which the frequency modulated beams are wavelength division multiplexed, the receiver comprises a detecting arrangement (26, 33-34) for detecting one of the channel discrimination signals in the information carrying intermediate frequency signal in correspondence to one of the channels that should be received as the selected channel. Besides a receiver circuit (21-25) and a level detector (31), the receiving arrangement comprises a scrambling (32, 35, 36) and a sweeping (35, 37, 38) arrangements.

Coherent homodyne optical communication receivers with photorefractive optical beam combiners

Abstract: The principles of operation and the results of performance measurements are reported of a new type of coherent optical receiver that used a dynamic volume index of refraction grating formed inside a photorefractive material to coherently combine signal and local oscillator light prior to photodetection. Because the refractive index grating is formed by the interference pattern generated where mutually coherent optical beams overlap, the receiver can automatically adjust to changes in angle of arrival or optical wavefront profiles which occur on time scales longer than the grating formation time. The grating appears stationary to high-speed phase modulation imposed on the signal beam and coherently diffracts local oscillator light into the signal beam direction. Performance measurements are reported for a prototype system that used two independent Nd:YAG lasers at 1.064 /spl mu/m, an iron-doped indium phosphide photorefractive crystal, and a four-slot phase modulation signal format. A receiver BER of 10/sup -6/ was obtained at received signal powers that corresponded to an average of 70 detected signal photons per bit at a source data rate of 50 Mb/s, 130 detected signal photons/bit at 220 Mb/s, and about 400 detected signal photons/bit at a 325 Mb/s source data rate. Quantum-limited operation corresponds to an average of six detected signal photons per transmitted information bit for this signal format. >

Parametric amplification of a polychromatic image

Abstract: The picosecond parametric amplification of a polychromatic image with a wavelength bandwidth of 140 nm and a gain of 15 dB has been obtained in a type I, LBO crystal. Thirty per 30 points were resolved. These results are in good agreement with a numerical study of the phase-matching conditions around the collinear degeneracy where phase-matching is non- critical for the signal beam in angle as well as in wavelength.