Abstract: A fluorescent light microscope for measuring a sample comprises a light source providing transfer light having a transfer wavelength for transferring a fluorescent dye in the sample from one state into another state, and a detector which measures fluorescent light from the sample with spatial resolution. The light source comprises a laser, an optical wave guide connected to the laser, and a wavelength-selective device connected to the optical wave guide. The laser emits pump light of a pump wavelength other than the transfer wavelength and injects the pump light into the optical wave guide.

Abstract: An embodiment relates to a device comprising an optical pipe comprising a core and a cladding, the optical pipe being configured to separate wavelengths of an electromagnetic radiation beam incident on the optical pipe at a selective wavelength through the core and the cladding, wherein the core is configured to be both a channel to transmit the wavelengths up to the selective wavelength and an active element to detect the wavelengths up to the selective wavelength transmitted through the core. Other embodiments relate to a compound light detector.

Abstract: A detector includes a light detecting layer and a grating structure. The light detecting layer, which can be a photodiode, has an optical mode that resonates in the light detecting layer, and the grating structure is positioned to interact with the optical mode. The grating structure further couples incident light having a resonant frequency into the optical mode, and causes destructive interference to prevent light having the resonant frequency from escaping the detecting layer. The light detecting layer can be made transparent to light having other frequencies, so that a stack of such detectors, each having a different resonant frequency, can be integrated into a WDM detector that is compact and efficient.

Abstract: The present invention relates to a method and device for reducing the phase noise of a laser signal from a laser source. This device comprises a first current generator for supplying a driving current to the laser source in view of producing the laser signal. A phase noise detector is responsive to the laser wavelength for generating a phase error signal and a second current generator is responsive to the phase error signal for generating a compensation current added to the driving current supplied to the laser source for generating a phase-adjusted laser signal. The device therefore defines a phase stabilization loop formed by the phase noise detector and the second current generator, for reducing the phase noise of the laser signal.

Abstract: A biological agent detector for detecting predetermined biological agents. The biological agent detector includes an optical fiber, a cladding that clads a length of the optical fiber and a bioindicator disposed within the cladding. The biological agent detector also includes a coherent light source that excites the optical fiber and a biological agent signature detector that detects the presence of a biological agent based upon a change in a resonance characteristic of the optical fiber caused by absorption of the predetermined biological agent into the cladding of the fiber.

Abstract: An optical antenna assembly including multiple optical antenna elements, each of the optical antenna elements are arranged in a regular pattern and carried by a supporting body. The regular pattern of the plurality of optical antenna elements is nonuniform. Certain ones of the optical antenna elements are configured to respond to the one or more waves of light.

Abstract: An optical receiving apparatus that receives an optical signal and outputs a data value of digital data transmitted by the optical signal is provided, including a light receiving element that receives the optical signal and outputs a photocurrent according to a strength of the optical signal, a present cycle integrator that integrates the photocurrent corresponding to a present cycle of the digital data over a prescribed period within the cycle, a previous cycle integrator that integrates the photocurrent corresponding to a cycle prior to the present cycle over a period that is substantially equal to the prescribed period in the cycle, and a data value identifying circuit that outputs a data value of the present cycle of the digital data based on a difference between a charge amount obtained through integration by the present cycle integrator and a charge amount obtained through integration by the previous cycle integrator.

Abstract: Methods and apparatus enable compensation of source light wavelength fluctuations due to instability of a broadband source within an optical sensing system. Tapping off two or more portions of the light output from the source at specific wavelength bands enables power based measurements of these portions. The measurements provide compensation ability by either use as feedback to control the source or for determination of the central wavelength so that adjustments can be applied to sensor response signals received at a receiver.

Abstract: Methods and apparatus enable compensation of source light wavelength fluctuations due to instability of a broadband source within an optical sensing system. Tapping off two or more portions of the light output from the source at specific wavelength bands enables power based measurements of these portions. The measurements provide compensation ability by either use as feedback to control the source or for determination of the central wavelength so that adjustments can be applied to sensor response signals received at a receiver.

Abstract: An apparatus and method for detection of peak wavelength values of colorimetric resonant optical biosensors using tunable filters and tunable lasers is provided. Biomolecular interactions may be detected on a biosensor by directing collimated white light towards a surface of the biosensor. Molecular binding on the surface of the biosensor is indicated by a shift in the peak wavelength value of reflected or transmitted light from the biosensor, while an increase in the wavelength corresponds to an increase in molecular absorption. A tunable laser light source may generate the collimated white light and a tunable filter may receive the reflected or transmitted light and pass the light to a photodiode sensor. The photodiode sensor then quantifies an amount of the light reflected or transmitted through the tunable filter as a function of the tuning voltage of the tunable filter.

Abstract: A chirp measurement apparatus includes a splitting section for splitting input signal light to two paths; a first dispersion medium with a total dispersion amount of +D (?0) at a used wavelength, and a second dispersion medium with a total dispersion amount of ?D (?0) at the used wavelength; first and second nonlinear photo-detecting sections for receiving the signal light beams passing through the first and second dispersion media, and for outputting electric signals with the intensities proportional to nth power of the intensities of the signal light beams, where n is greater than one; and a difference detecting section for computing a difference between the electric signals output from the first and second nonlinear photo-detecting sections, and for outputting a differential signal corresponding to the difference as a chirp signal of the input signal light.

Abstract: Disclosed herein are systems and methods for improving the performance of a luminescent concentrator. Performance may be enhanced by incorporating a reflector capable of blocking re-emitted photons from the luminescent material used to make frequency down conversion with a narrow reflection band, while allowing broad transmission of incident sunlight. The reflection band of the reflector that spectrally matches to the bandwidth of re-emission from the luminescent material acts as a luminescence cavity to prevent the outgoing re-emission that cannot be waveguided by total internal reflection to the photovoltaic device(s) located at the side edges of the concentrator.

Abstract: A photoelectric oscillator includes a laser beam projection unit; an optical modulator on an optical path extending from the projection unit, which optical modulator outputs a modulated signal or an optical signal containing a harmonic of the modulated signal and includes a modulation electrode whose resonant frequency band includes the frequency band of the modulation signal; a photoelectric converter for converting the output of the optical modulator to an electric signal; a feedback circuit for selecting from the radio-frequency electric signal obtained from the photoelectric converter an electric signal to be re-supplied to the optical modulator; and an output section for outputting an optical signal containing the modulation signal or a harmonic of the modulation signal or outputting the modulation signal or a harmonic of the modulation signal.

Abstract: A multi-spectrum image capturing device includes a multi-spectrum illuminating device comprising LED's for emitting lights of different wavelengths from one another, a plurality of optical rods for relaying the lights emitted from the LED's, an optical diffusion element for diffusively reflecting the lights from the optical rods by a white diffusion surface and an aluminum-coated reflecting surface to be irradiated at an angle of about 60° with respect to an image-capturing optical axis, and an optical sheet for further diffusing the lights from the optical diffusion element, and also includes an image-capturing optical system and a CCD for forming an image based on lights reflected from an irradiated surface under illumination by the multi-spectrum illuminating device to capture the formed image. An image output captured by the CCD is analyzed to measure color components of the irradiated surface.

Abstract: System, devices and methods are described that provide an integrated optical decombiner or optical combiner having both unamplified paths and amplified paths on which power monitoring and control may be located. A preferred multiplexing/demultiplexing optical path through the combiner/decombiner and a corresponding waveguide output/input is identified and optically coupled to a piece of fiber. Temperature control may be provided to tune an arrayed waveguide grating within the combiner/decombiner and minimize wavelength drift therein. Integrated power monitoring may be employed on one or more of the amplified waveguide paths to ensure that a preferred power level or range is maintained on an optical signal.

Abstract: A method and device are presented for use in determining a rate of rotation of an object. The device comprises a light guide comprising an arrangement of a plurality of coupled optical resonators arranged along a curvilinear optical path. This allows for determining a change in at least one of the light phase and frequency affected by the light propagation through the curvilinear path during the device rotation, said change being indicative of the rotation rate of the light guide.

Abstract: An optical sensing system uses light scattered from a sensing fibre to sense conditions along the fibre, and has a receiver with a frequency to amplitude converter to obtain a frequency of a Brillouin component of the received scattered light, to deduce the conditions. This converter can avoid time consuming scanning of frequencies to obtain the Brillouin frequency spectrum, and avoids the heavy processing load of deducing a peak or average frequency from the spectrum. The converter can be implemented in the optical domain using a grating or interferometer, or in the electrical domain using a diplexer or electrical interferometer. It can generate complementary signals, having opposite signs, a ratio of these signals representing the frequency. This can avoid sensitivity to amplitude changes in the received scattered signals and provide common mode rejection of noise.

Abstract: An optical accelerometer includes means for changing the length of at least one optical fiber in response to acceleration functionally coupled to the at least one optical fiber. The fiber and the means for changing length are enclosed in a pressure compensated housing. The housing is filled with a substantially incompressible fluid or gel.

Abstract: A monitoring system has the capability to monitor multiple signal bands simultaneously. Specifically, in one embodiment, the monitoring system can simultaneously monitor the C- and L-bands. As a result, the time to scan through the spectral band can be reduced by half. The system comprises a signal source for an optical signal having spectrally separated channels distributed within a first spectral band and a second spectral band. A tunable filter filters this optical signal. A dichroic filter separates the first spectral band from the second spectral band in the optical signal, which has been filtered by the tunable filter. Thereafter, first and second optical detectors detect the respective spectral bands to the filtered optical signal.

Abstract: The present invention discloses a fiber Bragg grating sensor system.

Abstract: Automatic background signal removal for input data, such as for spectrometry data, is provided. Input data includes input pixel points, such as those read by a CCD spectrometer or chromatography device, and intensity values corresponding to the data points. A distribution of changes in the intensity values between the data points is determined, and a noise level is judged by setting a threshold for the distribution. A noise region is identified as a predetermined number of consecutive input points for which the changes in the intensity values are within the noise level. Adjacent noise regions may be connected and the background signal is thus determined and subtracted. A spike noise region may also be identified and filtered, such that a peak obtained from fewer than a second predetermined number of the pixel points is determined as a spike, not a true peak. Non-spike large amplitude noises are optionally filtered.

Abstract: A wear determination device for determining vibration in a turbine engine component to reduce wear in a turbine engine. The wear determination device may be capable of measuring vibrations in a turbine engine component. The vibration measurement may be used to determine vibrations in a turbine engine to identify wear locations and sources of wear. The wear determination device may be configured such that multiple locations in a turbine engine may be monitored on a single turbine engine by moving the wear determination device from location to location.

Abstract: Methods for utilizing optical systems in order to introduce digitally tunable amounts of temporal dispersion into optical signals and methods and systems for providing angular dispersion compensated output from optical switching/routing systems.

Abstract: An apparatus for measuring coherent crosstalk (CXT) light of the invention generates in a light source section, measurement light which has been modulated to a sawtooth wave shape and applies this to an object of measurement; sends transmission light and CXT light emerging from the object of measurement to a light receiving section via a variable optical attenuator; applies an electrical signal photoelectric-converted in an optical receiver, to a frequency filter, to thereby extract a beat component corresponding to a frequency difference between the transmission light and CXT light; controls the modulation period of the measurement light so that the power of the beat component becomes a local maximum; varies an optical attenuation amount of a variable optical attenuator, while keeping constant the optimized modulation period; and measures with high accuracy the amount of CXT light generated in the object of measurement, based on a rate of variation in the power of the beat component caused at that time.

Abstract: An optical transducer includes a light emitting unit, a light detecting unit, light radiating sensor heads and light receiving sensor heads; the light radiating sensor heads and light receiving sensor heads are alternately arranged at intervals, and moving objects pass through the intervals in such a manner as to intersect light beams between the sensor heads; since the light emitting unit and light detecting unit are remote from the sensor heads, the light emitting unit and light detecting units are optically coupled to the sensor heads through optical fibers; a bundle of optical fibers is clipped on a predetermined route, and the optical fibers swerve from predetermined points of the bundle so that the optical fibers are surely warped so as to exert the resilient force on the inner surfaces of the optical devices, thereby being kept stable during the adhesion therebetween.

Abstract: Apparatus (10) for measuring absolute specular reflectance of a surface of a sample (22) includes a sample holder (12), a light source (18) for transmitting an incident light beam (16) onto a surface of the sample (22) and a detector (26 ) for detecting a specularly reflected component of the incident light. The light source (18), sample holder (12) and detector (26) are mounted and operatively associate (14, 24, 28) to be relatively moveable to vary the angle of incidence of light (16) onto sample (22) and to correspondingly automatically vary the relative position of the detector (26) such that the angle of reflection equals the angle of incidence. In the absence of the sample (22) or upon removal of the sample holder (12), light (16) impinges directly onto detector (26) to directly allow measurement of the absolute intensity of the light beam (16) as a reference measurement. This avoids the need to use intervening optical components such as mirrors which may degrade over time.

Abstract: An optical wavelength readout system for application in optical sensing systems is disclosed. The system includes a Master unit including a wavelength swept optical source for launching light into a string of optical sensors, and a detection and processing unit for detecting and processing the light emitted by the source. The system also includes a Slave unit including a light coupling device for coupling light from the light source into the string of sensors and for coupling light reflected from the string of sensors to a detection and processing unit arranged to detect and process the reflected light. The Master unit includes a wavelength reference unit adapted to make a reference signal available to other parts of the sensing system. The reference signal represents a generally exact relation between the wavelength of the light emitted from the source and time.

Abstract: An optical wavelength readout system for application in optical sensing systems is disclosed. The system includes a Master unit including a wavelength swept optical source for launching light into a string of optical sensors, and a detection and processing unit for detecting and processing the light emitted by the source. The system also includes a Slave unit including a light coupling device for coupling light from the light source into the string of sensors and for coupling light reflected from the string of sensors to a detection and processing unit arranged to detect and process the reflected light. The Master unit includes a wavelength reference unit adapted to make a reference signal available to other parts of the sensing system. The reference signal represents a generally exact relation between the wavelength of the light emitted from the source and time.

Abstract: A system and method for monitoring all the characteristic parameters of a DWDM communication system is implemented with two variants. Firstly, this is achieved by means of a specific grating spectrometer displaying a high resolution and a high-speed sampling of the measured values, and secondly by the application of an opto-electronic cross correlator as a purely electronic solution. The grating spectrometer is expediently a particular system in a mixed array according to Ebert and Fastie, wherein the light to be measured passes four times through the grating in a specific manner. The opto-electronic cross correlator can mix the working light with a reference light tunable in terms of its frequency to form an electrical low-frequency signal that is analyzed in a high-impedance operation.

Abstract: A bond separation inspection method using an optical fiber sensor. The method includes a step of embedding a sensor part of an optical fiber sensor in an adhesive joining a plurality of members together. The sensor part is embedded in the adhesive in such a way that the sensor part undergoes a compressive strain. Separation of the bond is detected on the basis of an optical characteristic of the sensor part when light from a light source is directed into the optical fiber sensor.

Abstract: A system for detecting dispersion in an incoming optical signal centered about a channel center frequency. The system includes a splitter unit for separating the incoming signal into first and second groups of signals. The system further includes a first compensation region adapted to apply a desired positive dispersion characteristic to a signal in the first group and a second compensation region adapted to apply a desired negative dispersion characteristics to a signal in the second group. The splitter also includes a receiver unit connected to the first and second compensation regions, and adapted to compare the received signals and to detect the dispersion in the incoming optical signal on the basis of the comparison. The system can be selectively balanced at different optical frequencies by varying the amount of dispersion applied by the first and second compensation regions.

Abstract: A chirp measurement apparatus includes a splitting section for splitting input signal light to two paths; a first dispersion medium with a total dispersion amount of +D (?0) at a used wavelength, and a second dispersion medium with a total dispersion amount of ?D (?0) at the used wavelength; first and second nonlinear photo-detecting sections for receiving the signal light beams passing through the first and second dispersion media, and for outputting electric signals with the intensities proportional to nth power of the intensities of the signal light beams, where n is greater than one; and a difference detecting section for computing a difference between the electric signals output from the first and second nonlinear photo-detecting sections, and for outputting a differential signal corresponding to the difference as a chirp signal of the input signal light.

Abstract: Prior art wavelength lockers used in tunable laser systems can provide information to ensure that the laser is locked onto a channel, but do not provide information as to which specific channel the laser is locked onto. Embodiments of the present invention include a wavelength locking channel monitor that provides a servo-locking error signal and a channel-identifying signal to allow a tunable laser to be updated to lock to the proper channel. Embodiments of the present invention include wavelength-dependent periodic and/or monotonic filters, which provide monotonically variable finesse and a monotonically variable transmission. Embodiments of the present invention also extracts amplitudes, phases, frequency, and/or modulation depths from a dither introduced in an incident light beam to determine the laser channel and the laser mode within that channel.

Abstract: A source and/or method of generating quantum-correlated and/or entangled photon pairs using parametric fluorescence in a fiber Sagnac loop. The photon pairs are generated in the 1550 nm fiber-optic communication band and detected by a detection system including InGaAs/InP avalanche photodiodes operating in a gated Geiger mode. A generation rate>103 pairs/s is observed, a rate limited only by available detection electronics. The nonclassical nature of the photon correlations in the pairs is demonstrated. This source, given its spectral properties and robustness, is well suited for use in fiber-optic quantum communication and cryptography networks. The detection system also provides high rate of photon counting with negligible after pulsing and associated high quantum efficiency and also low dark count rate.

Abstract: A fiber optic sensor system comprises at least one measuring sensor 1 providing an optical output dependent upon one or more parameters to be measured, e.g. temperature, and at least one reference sensor 2 providing a reference output for comparison with the measuring sensor output. The reference sensor is provided in a birefringent fiber. The system includes a detecting means 13,14 whereby a reference beat signal f2 is derived by measuring the optical frequency splitting between frequency components in different polarization planes of the reference sensor output. A further beat signal f3 is generated between the measuring and reference sensor outputs, such beat signals being used to derive a measurement of one or more parameters.

Abstract: Systems for detection and compensation of modal dispersion in an optical fiber system including a multisegment photodetector coupled to an end of an optical fiber for detecting optical signals exiting the optical fiber and for converting the optical signals to an electrical output are provided. A representative multisegment photodetector includes a plurality of photodetector regions configured such that each of the plurality of photodetectors detects a portion of the plurality of optical signals exiting the end of the optical fiber and modifies the signal to reduce the affects of modal dispersion. Other systems are also provided.

Abstract: A tunable filter may be utilized to successively tune to different wavelengths. As each wavelength of the wavelength division multiplexed signal is extracted, it may be successively power monitored. Thus, power monitoring may done without requiring separate power monitors for each channel. This results in considerable advantages in some embodiments, including reduced size, reduced complexities in fabrication, and reduced yield issues in some embodiments.

Abstract: In the present invention an optical waveguide grating sensing device for a dual-parameter optical waveguide grating sensor includes a first optical waveguide grating of a first resonant wavelength provided in a first section of an optical waveguide and a second optical waveguide grating of a second resonant wavelength provided in a second of an optical waveguide. The first and second gratings have different coefficients of rate of change of wavelength as a function of temperature and have substantially the same coefficient of rate of change of wavelength as a function of stain.

Abstract: A reflected light from a Bragg grating in an electrical transformer or other apparatus at which temperature is to be measured, is positioned by an optocoupler through a second fiber provided with a second Bragg grating whose reflection wavelength is different from that of the first grating. The nonreflected light intensity is measured by a photodetector and is used to signal the temperature measurement.

Abstract: A measurement apparatus for an optical signal under test includes a closed-loop optical path, an optical mixer in the closed-loop optical path and a photodetector. The optical signal under test and sampling light having a wavelength different from that of the optical signal under test are circulated in the closed-loop optical path. Sum/difference frequency light is generated every time the sampling light passes through the optical mixer. The sum/difference frequency light is detected by the photodetector, which provides a signal representative of the waveform of the optical signal under test.

Abstract: Prior art wavelength lockers used in tunable laser systems can provide information to ensure that the laser is locked onto a channel, but do not provide information as to which specific channel the laser is locked onto. Embodiments of the present invention include a wavelength locking channel monitor that provides a servo-locking error signal and a channel-identifying signal to allow a tunable laser to be updated to lock to the proper channel. Embodiments of the present invention include wavelength-dependent periodic and/or monotonic filters, which provide monotonically variable finesse and a monotonically variable transmission. Embodiments of the present invention also extracts amplitudes, phases, frequency, and/or modulation depths from a dither introduced in an incident light beam to determine the laser channel and the laser mode within that channel.

Abstract: A highly reliable optical add/drop device is described. The optical add/drop device has an external tube and a ring, wherein the external tube and the ring are made of metallic material. A WDM filter is fixed in the ring. The ring is inserted in the external tube at the middle portion and fixed therein by soft solder technique. A single fiber collimator and a dual fiber collimator are respectively coupled with the opposite surfaces of the filter, and aligned in the external tube. Additionally, the single and dual fiber collimators are also fixed therein by soft solder technique, as two metal tubes respectively hold the single and dual fiber collimators. In the invention, the WDM filter is rigidly fixed to avoid tilting during temperature variation. Moreover, the invention provides an optical add/drop device with low insertion loss and reflection loss.

Abstract: High-resolution measurement of a parameter is provided at multiple different locations simultaneously along an optic fiber. Light within a predefined range of wavelengths is transmitted into an optic fiber that contains multiple birefringent fiber optic pressure transducers, each including a Fiber Bragg Grating. Each grating defines a spatially modulated index of refraction and a wavelength that is unique within the system. A sweeping comb filter is used to apply optical comb filtering to light reflected from the transducers so as to pass filtered light having multiple spectral portions, each spectral portion associated with one transducer. The free spectral range of the sweeping comb filter is set to be approximately equal to the spectral range of a single spectral portion. Wavelength division multiplexing is applied to the filtered light so as to separate the spectral portions.

Abstract: An optical interrogation system 10 includes optical amplifying and gating apparatus, in the form of a semiconductor optical amplifier (SOA) 14 and an optical source 12, 14. Drive apparatus 22 (an electrical pulse generator driven by a variable frequency oscillator) is provided to generate electrical drive pulses (see inset (a)) which are applied to the SOA 14, to cause the SOA 14 to switch on and off. The optical source comprises a super-luminescent diode (SLD) 12, the CW output from which is gated into optical pulses by the SOA 14. The SOA 14 is optically coupled to the waveguide 16 containing an array of reflective optical elements (gratings G) to be interrogated. The interrogation system further includes an optical detector 18, optically coupled to the SOA 14, operable to evaluate the wavelength of a returned optical pulse transmitted by the SOA 14.

Abstract: The specification describes a wavelength monitoring system for multiple wavelength communications systems, such as WDM systems, based on the recognition that the mechanism for spatially separating the individual wavelength bands can be achieved within the optical fiber itself. Individual wavelength bands are separated using a series of discrete gratings spaced longitudinally along the fiber core. The wavelength bands are extracted from the fiber core by converting the energy in the selected band from a core-guided mode to a radiation mode. By using a tilted grating, the light in the radiation mode is directed through the cladding and out of the fiber. Spatial resolution of the selected bands can be any desired physical length. An important implication of this is that detection can be made in the near field using inexpensive detecting apparatus.

Abstract: A wavelength selective detector having a first absorbing layer for absorbing light with a wavelength below a lower band cutoff, a second absorbing layer downstream of the first absorbing layer for absorbing light with a wavelength below an upper band cutoff, and a confinement layer situated between the first and second absorbing layers. The lower and upper band cutoffs can be set by controlling the bandgaps and/or thicknesses of the first and second absorbing layers. The wavelength selective detector of the present invention has a good out-of-band rejection, a narrow spectral responsivity, and a high in-band responsivity. In addition, the wavelength selective detector is relatively easy to manufacture using conventional integrated circuit fabrication techniques.

Abstract: An optical autocorrelator comprises an optical waveguide (40) of semiconductor material which exhibits two photon absorption at a wavelength at which the autocorrelator is intended to operate. Reflecting means (46) are provided at a part of the waveguide which is remote to an end (42) in which an optical pulse (44) is input for reflecting the optical pulse such as to generate counter-propagating optical pulses in the waveguide. A plurality of electrodes (481-48N) are disposed along the waveguide for measuring a two photon absorption photocurrent (i1-in) generated in the waveguide by the counter-propagating optical pulses.

Abstract: Fibre optic apparatus for accurate and repeatable measurements of light comprising one or more wavelength ranges, and system employing the apparatus. The apparatus according to the invention comprises: a directional coupler adapted to lead the light into an optical fibre, said optical fibre containing at least one analysis filter for each wavelength range, said analysis filters consisting of at least one fibre-optical Bragg-grating (FBG) which reflects incident light with a chosen wavelength back through said directional coupler and onto a detector having an associated signal processing unit, a modulator device for pulsing the incident light with a chosen pulse width, and an optical fibre delay line in front of each analysis filter, with a length adapted to provide for a sufficient time delay larger than the pulse width, so that the pulses reflected from each analysis filter at different wavelengths can be separated in time and thereby be demodulated in the signal processing unit.

Abstract: Apparatus and method for measuring scatterer size in a dense media with only a single fiber for both light delivery and collection are disclosed. White light is used as a source and oscillations of the detected light intensities are measured as a function of wavelength. The maximum and minimum of the oscillations can be used to determine scatterer size for monodisperse distributions of spheres when the refractive indices are known. In addition several properties of the probe relevant to tissue diagnosis are disclosed including the effects of absorption, a broad distribution of scatterers, and the depth probed.

Abstract: A laser difference frequency discriminator that detects the difference between two laser frequencies and outputs a voltage near baseband that is related to the difference frequency. This discriminator power splits a laser beam containing the two laser frequencies into two paths, one which is sent down a delay line to a photo detector while the other is sent directly to a photodiode; there may be an optional phase shifter in either path. The relative phases of the heterodyne signals from the photo detectors are compared in a phase detector, its output voltage is related to the phase difference, which is, in turn, related to the difference frequency. This discriminator has applications in microwave generation, laser radar, and optical communications.