Abstract: The present invention provides a multi-functional separator which may be used as a demultiplexer or as a multiplexer in wavelength division multiplexed optical communication systems. The preferred embodiment of the multi-functional separator includes a first polarization beam splitter, a non-reciprocal rotator; a reciprocal rotator, a second polarization beam splitter, and a non-linear interferometer. Each of the polarizing input and polarizing output ports includes an optical fiber, a collimator, a birefringent walk-off plate and a non-reciprocal optical rotator. The multi-functional separator is easily aligned by adjusting the positions of each of the polarizing input and output port. Further embodiments of the present invention provide additional optical isolation, optical circulation, optical comb filtering and/or two-stage channel separation capabilities.

Abstract: The present invention provides an interferometer. In one embodiment, the interferometer includes a translucent body having a first portion and a second portion, where the second portion has at least three internal reflective sides. The interferometer also includes an interface between the first and second portions, configured to reflect a portion of an optical signal received through the first portion and transmit a remaining portion of the optical signal into the second portion. Also disclosed are a method of manufacturing an interferometer and a transmitter incorporating the interferometer or the method.

Abstract: The present invention provides an apparatus for determining a wavelength of an optical signal by determining a coarse wavelength response and a fine wavelength response. The coarse wavelength response is achieved by utilizing an optical filter. A suitable detector detects the wavelength-dependent response and conveys the determined coarse wavelength response to the processing logic. The fine wavelength response is achieved by utilizing an interferometer that is capable of generating an interference pattern. Two detectors are disposed in the interference pattern at a quadrature separation from each other and detect the intensity responses at their respective locations. The intensity responses are conveyed to a unit that determines the fine wavelength response. Finally, the processing logic determines the wavelength utilizing the determined coarse wavelength response and the determined fine wavelength response.

Abstract: An interferometer is used to provide control to the intensity profile and position of a spot of light. In this invention, each light ray from a spectral source is regenerated into a plurality of light rays by an interferometer. These rays are focused by a lens into a constructive interference fringe on a focal plane. A voltage across the interferometer can change the index of reflection of the interferometer thus defines the position of the constructive interference fringe on the disk.

Abstract: A bandwidth meter method and apparatus for measuring the bandwidth of a spectrum of light emitted from a laser input to the bandwidth meter is disclosed, which may comprise an optical bandwidth monitor providing a first output representative of a first parameter which is indicative of the bandwidth of the light emitted from the laser and a second output representative of a second parameter which is indicative of the bandwidth of the light emitted from the laser; and, an actual bandwidth calculation apparatus utilizing the first output and the second output as part of a multivariable equation employing predetermined calibration variables specific to the optical bandwidth monitor, to calculate an actual bandwidth parameter.

Abstract: An airgap type etalon has a higher degree of design freedom of a wavelength-temperature characteristic so that such a wavelength-temperature characteristic can be freely adjusted. The airgap type etalon includes a fixing block having one flat surface, and a transparent parallel flat plate having parallel flat surfaces formed with an antireflection coating and a reflection augmenting coating thereon, respectively. The flat surface at the antireflection coating side is joined to the flat surface of the fixing block. A parallel flat spacer has a thickness greater than that of the transparent parallel flat plate and an expansion coefficient different from that of the transparent parallel flat plate. One of the flat surfaces of the parallel flat spacer is joined to the flat surface of the fixing block. A transparent flat plate has opposite flat surfaces formed with an antireflection coating and a reflection augmenting coating thereon, respectively.

Abstract: Methods and apparatus for chromatic dispersion compensation are provided. The apparatus includes a Gires-Tournois etalon, an optical beam separator, a GTE controller, an optical distortion analyzer, and a feedback controller.

Abstract: A method of finding drive values for an actuation mechanism having three degrees of freedom is provided, that will optimize a predetermined parameter of a system that utilizes the actuation mechanism. In one embodiment, a method of finding drive values for a tunable Fabry-Perot cavity is provided, for driving three independently adjustable actuators such that the cavity mirrors of the tunable Fabry-Perot cavity are maintained in a substantially parallel relationship.

Abstract: A polarization independent optical spectrum analyzer comprises an inherently polarization sensitive angle-tuned filter element and polarization-maintaining multi-pass optics for directing a light beam to and fro through the tunable filter element while maintaining its linear state of polarization. The optical spectrum analyzer comprises such a tunable optical filter in combination with a polarization control unit for decomposing a light beam for analysis into first and second beams having mutually orthogonal states of polarization (SOPs) and then adjusting one or both SOPs so that they are parallel to each other and to one of the principal axes of the angle-tuned filter which selects different wavelengths of the first and second light beams. The first and second light beams are passed through the filter repeatedly by multi-pass polarization-maintaining optics.

Abstract: An optical spectrum analyzer apparatus for analyzing the spectral content of a light signal. The optical spectrum analyzer apparatus includes an optical tapped delay line (OTDL) unit as a light dispersing unit to provide an analyzer apparatus having increased resolution.

Abstract: A process for tunable filter train alignment comprises detecting a spectral response of the filter train and aligning an optical fiber that transmits an input optical signal to the filter train during operation. Further, the tunable filter is moved relative to the filter train in response to a spectral response of the filter train. As a result, the alignment and spectral response of the tunable filter train are optimized. In the preferred embodiment, the alignment and SMSR optimization occur simultaneously with respect to each other.

Abstract: Apparatus and methodology by which the radius of curvature of individual optics may be determined through the interferometric measurement of the optical length of a spherical cavity established from null tests of combinations of the individual optics and an algorithm that mutually intercompares the measured cavity lengths and radii of curvature of the individual optics.

Abstract: This invention provides a method and an optical system for sensing and controlling the frequency for a laser with respect to an optical cavity and for sensing and controlling the length difference of interferometer paths in a two beam interferometer. A misalignment is introduced in the incident laser radiation to produce a fundamental mode (TEM00) in the cavity or interferometer and the reflection of a least one higher order mode (TEM01). A split photodetector (10) allows the interference between these two modes to be measured separately by detecting two spatially distinct portions of the single reflected beam. An error signal indicative of the difference between the fundamental mode frequency and the cavity resonant frequency is obtained by substracting the outputs from the two parts of the photodetector.

Abstract: A GTIFR interferometer, for use in an interleaver or in a deinterleaver, wherein the GTIFR interferometer includes a Gires-Toutnois interferometer with a 45 degree Faraday rotator between the mirrors of the Gires-Tournois interferometer and further includes a 22.5 degree Faraday rotator in the light path to the Gires-Tournois interferometer and an interleaver or deinterleaver that contains one GTIFR. A dispersion compensated GTIFR interleaver includes a second Gires-Tournois interferometer for providing chromatic dispersion compensation.

Abstract: Optical filter elements and optical systems comprise optically mismatched etalons and optically mismatched stacked, optically coupled etalons that are directly optically coupled, at least one of the etalons or stacked, optically coupled etalons comprising first and second selectively transparent thin film mirror coatings on opposite surfaces of a bulk optic. The optically mismatched etalons can be configured to selectively pass single passbands. The disclosed optical systems optionally comprise other devices optically coupled to the optically mismatched etalons and optionally mismatched stacked, optically coupled etalons.

Abstract: An optical configuration that provides tunable characteristics. The tunable characteristics are applicable, for example, for channel monitoring, dispersion compensation and polarization-dependent loss. A passive optical element is used where the optical properties of this element varies as a function of position on the element.

Abstract: An optical frequency discriminator includes an interferometer cascaded with an absorption cell that provide a composite signal. A receiver samples a composite signal and maps to the sample positions of the acquired samples, corresponding optical frequencies of an applied optical signal.

Abstract: A method and system for performing swept-wavelength measurements within an optical system provides improved operation in resonator-enhanced optical measurement and data storage and retrieval systems. The system includes an illumination subsystem having a swept-wavelength mode, a detection subsystem, an interferometer or an optical resonator interposed in an optical path between the illumination subsystem and the detection subsystem and a time domain analysis subsystem. Multiple resonance points of the optical resonator are detected by the time-domain subsystem when the illumination subsystem is in the swept-wavelength mode in order to determine resonator or interferometer characteristic changes. The resulting information can be used directly as a measurement output, or cavity length information may also be used to adjust the operating wavelength of a constant wavelength mode of the illumination subsystem.

Abstract: A method and apparatus for stretching a pulse, shaping a stretched pulse, and modeling a stretched and/or shaped pulse are disclosed. An etalon has a port, a partially reflective surface, and a fully reflective surface. A base pulse is introduced into the etalon, and a plurality of portions of the base pulse propagating from the etalon are collected. The collected portions are then combined to generate a stretched pulse whose width is proportional to the width of the base pulse. This can be modeled by assigning a transmission factor value to each one of a plurality of taps and a reflection factor value to each one of the taps, excepting only one tap. A transport delay for is assigned to each tap to which a reflection factor value was assigned, wherein the transport delay is proportional to the width of a base pulse.

Abstract: Within a Fabry-Perot filter apparatus, a method for fabricating the Fabry-Perot filter apparatus and a method for operating the Fabry-Perot filter apparatus, there is employed a Fabry-Perot filter and at least one color filter layer, both assembled over a substrate and covering at least two optical transducer elements which are formed within the substrate. Within the foregoing apparatus and methods, the at least one color filter layer comprises at least two color filter elements of separate color, each registered with a separate optical transducer element within the at least two optical transducer elements. The apparatus and methods provide for enhanced optical discrimination properties.

Abstract: According to an aspect of the present invention, a circuit is provided for determining the wavelength and power of a given optical signal across a wide dynamic range. The wavelength and power determinations are performed by logarithmic ratio amplifier in concert with a digital signal processor that utilizes representative equations of the measured optical signal.

Abstract: Interleavers, based on a Michelson interferometer with a Gires-Tournois (GT) etalon in each arm, are becoming popular in the filtering of light in the fiber optics telecommunications industry. As the channel spacing becomes closer together, e.g. 50 GHz or 25 GHz, dispersion compensation becomes an important factor in the choice and design of a system. The present invention solves the problem of increased chromatic dispersion by utilizing multi-cavity Gires-Tournois (MCGT) etalons, wherein the dispersion from one MCGT is used to compensate or cancel the dispersion from the other MCGT. In an optimum design for a dual cavity GT etalon, the dispersion profile of the first MCGT will have a similar amplitude and frequency as the dispersion profile of the second MCGT, only shifted by half the period so that the positive slopes of one profile are aligned with the negative slopes of the other profile.

Abstract: The present invention provides a wavemeter for an ultraviolet laser capable of long life beam quality monitoring in a pulsed ultraviolet laser system at pulse rates greater than 2000 Hz at pulse energies at 5 mJ or greater. In a preferred embodiment an enhanced illumination configuration reduces per pulse illumination of an etalon by a factor of 28 compared to a popular prior art configuration. Optics are provided in this embodiment which reduce light entering the etalon to only that amount needed to illuminate a linear photo diode array positioned to measure interference patterns produced by the etalon. In this preferred embodiment two sample beams produced by reflections from two surfaces of a beam splitter are diffused by a defractive diffuser and the output of the defractive diffuser is focused on two separate secondary diffusers effectively combining both beams in two separate spectrally equivalent diffuse beams.

Abstract: The present invention provides a relatively simple etalon testing system and process for measuring cavity error of etalons to high precision. It works equally well on solid and air-spaced designs. This invention should be a great aid in the manufacture of high performance etalons, separating out the geometric and reflectivity finesses. The present invention permits measurement of etalon spacings to an accuracy of better than &lgr;/1000 (i.e., about 63 picometers [6.3×10−11 m] when using a HeNe test laser). In a preferred process an etalon under examination is mounted on a rotational stage illuminated with a collimated beam from a HeNe laser. Reflections from the etalon are imaged on a screen to produce interference fringes which are monitored by a CCD camera. The etalon is then pivoted about an axis perpendicular to the laser beam and images of the interference patterns are recorded periodically to produce a plot of intensity vs.

Abstract: A wavelength locker having a first beam splitter to receive a light beam and separate out a portion as a sample beam; a confocal etalon to receive the sample beam and filter it into a filterization beam; a filterization photodetector to receive the filterization beam and produce a filterization signal representative of the light intensity in the filterization beam, and thus also of the light frequency in the filterization beam, sample beam, and original light beam; and a link to communicate a control signal, based on the filterization signal, to the light source producing the light beam to lock the wavelength or the frequency.

Abstract: An apparatus measures a spectral distribution of a narrow-band laser beam generated by a line-narrowed excimer laser or a molecular fluorine laser system. The apparatus includes an an interferometric device disposed along an optical path of an output beam of the laser system such that the beam traverses the interferometric device on a first pass, a retro-reflector disposed after the interferometric device along the optical path for retro-reflecting the beam back through the interferometric device on a second pass, and a detector for detecting an intensity of the beam after the second pass through the interferometric device. Preferably, spectral information is determined when the free spectral range of the interferometric device is tuned and the detector measures the intensity of the beam at a plurality of free spectral ranges or when the wavelength of the output beam is tuned.

Abstract: A detunable Fabry-Perot interferometer, and method of tuning a Fabry-Perot interferometer are provided. The Fabry-Perot interferometer includes a first mirror, a second mirror oriented with respect to the first mirror so as to define a Fabry-Perot cavity therebetween, and an actuator configured to adjust a resonant wavelength of the Fabry-Perot cavity by varying a gap between the first and second mirrors, wherein the actuator is configured to selectively maintain the first and second mirrors in a substantially non-parallel relationship while the resonant wavelength of the Fabry-Perot interferometer is varied. The detunable Fabry-Perot interferometer can be employed in a multiplexer of a telecommunications system, as provided.

Abstract: The present invention is a cost-effective and compact micro-spectrometer for rapid detection of chemical compounds in the low concentration limit. The invention provides for significantly higher sensitivity compared to conventional spectroscopy techniques (continuous wave and Fourier transform methods) by placing the sample within a high Finesse etalon cavity. An Optical Spectrum Analyzer (OSA) built on either continuous wave (CW-SPEC), or Fourier Transform Absorption Spectroscopy (FT-SPEC) is used to monitor the spectrum from the etalon cavity/sample combination during tuning of the etalon cavity˜this information is then used to reconstruct the absorption spectrum.

Abstract: The present invention provides an apparatus for determining a wavelength of an optical signal by determining a coarse wavelength response and a fine wavelength response. The coarse wavelength response is achieved by utilizing an optical filter. A suitable detector detects the wavelength-dependent response and conveys the determined coarse wavelength response to the processing logic. The fine wavelength response is achieved by utilizing an interferometer that is capable of generating an interference pattern. Two detectors are disposed in the interference pattern at a quadrature separation from each other and detect the intensity responses at their respective locations. The intensity responses are conveyed to a unit that determines the fine wavelength response. Finally, the processing logic determines the wavelength utilizing the determined coarse wavelength response and the determined fine wavelength response.

Abstract: A method and apparatus is provided for calibrating a Fabry-Perot etalon based optical measurement system. The calibration is performed by analyzing the shape of transmission peaks output from the etalon in response to a known optical signal and using that information, along with a formula that approximates the response of the etalon, to perform the calibration.

Abstract: The present invention discloses a Fabry-Perot device compensating for an error of full-width-at half-maximum (FWHM) and a manufacturing method for the device. The Fabry-Perot device mainly consisted of a Fabry-Perot resonant cavity for a light to pass through. The cavity includes a first reflecting surface with a first reflectance for partly reflecting the light, and a second reflecting surface with a second reflectance for partly reflecting the light. In addition, a distance between the first and second reflecting surfaces may be adjusted according to the first and second reflectance, and thereby compensating for the error of FWHM caused by the first and second reflectance.

Abstract: Wavelength reference apparatus for use in calibrating a tunable Fabry-Perot filter or a tunable VCSEL, whereby the device may be tuned to a precise, known wavelength, the wavelength reference apparatus comprising an LED, where the LED is chosen so as to have an emission profile which varies with wavelength; an etalon, where the etalon is chosen so as to have a transmission profile which comprises a comb of transmission peaks, with each transmission peak occurring at a precise, known wavelength; and a detector for detecting the light emitted by the LED and passing through the etalon; whereby when a tunable Fabry-Perot filter or tunable VCSEL is positioned between the etalon and the detector, and the device is swept through its tuning range by varying the tuning voltage applied to the device, the known transmission wavelengths established by the LED and the etalon can be correlated to counterpart tuning voltages of the device, whereby to calibrate the device.

Abstract: A method and system for controlling resonance within a resonator-enhanced optical system provides improved tracking performance in resonator-enhanced optical measurement and data storage and retrieval systems. The system includes an illumination subsystem and a detection subsystem with an optical resonator interposed in an optical path between the illumination subsystem and the detection subsystem. The resonance of the optical resonator is tuned, either by changing the wavelength of the illumination subsystem or the geometric path length within the resonator. Closed-loop feedback control signals can thereby maintain resonance at a desired operating point. The feedback control signal components can be further used to provide measurement data if the resonance of the optical resonator is a function of a measured surface, such as when a reflective surface of the resonator is a surface under measurement.

Abstract: The method and system operate to calibrate a transmission laser of the dense wavelength division multiplexer (DWDM) and to lock the laser to a selected transmission wavelength. In one example, the transmission laser is a widely tunable laser (WTL) to be tuned to one of a set of International Telecommunications Union (ITU) transmission grid lines for transmission through an optic fiber. To lock the WTL to an ITU grid line, a portion of the output beam from the WTL is routed through the etalon to split the beam into a set of transmission lines for detection by a detector. Another portion of the beam is routed directly to another detector. A wavelength-locking controller compares signals from the two detectors and adjusts the temperature of the etalon to align the wavelength of one of the transmission lines of the etalon with the wavelength of the output beam, then controls the WTL in a feedback loop to lock the laser to the etalon line.

Abstract: A multi cavity comb filter for interleaving or de-interleaving WDM signals has a plurality of stacked optical cavities each having substantially the same thickness. The multiple cavity arrangement provides a comb reflection response and a comb transmission response with broad peaks, so that the filter can be used for transmitting one group of channels and reflecting another group of channels at interleaved positions. The cavities are preferably formed from silicon wafers, so that existing techniques can be employed to obtain specific cavity thicknesses with sufficient accuracy and uniformity.

Abstract: In accordance with the invention, a electromechanical optical modulator comprising an optical membrane, a substrate and Fabry-Perot air gap between them is provided with an improved structure for controlling light transmitted into the substrate. Specifically, an etched and coated cavity is formed in the backwall of the substrate underlying the air gap to receive transmitted light and redirect it onto controllable paths within the substrate. Advantageously the substrate is silicon, and the cavity is produced by anisotropic etching.

Abstract: The present invention discloses a Fabry-Perot optical filter device, which includes a Fabry-Perot element for allowing a light to pass through and optically filtering the light at least twice, and at least one reflecting element for reflecting the light passed through the Fabry-Perot element back to the same Fabry-Perot element during the at least two optical filtering. The Fabry-Perot optical filter device further includes an input terminal used to import the light into the Fabry-Perot optical filter device, and an output terminal used to export the light after the at least two optical filtering.

Abstract: A transmission-type extrinsic Fabry-Perot interferometric optical fiber sensor and a method used for integrity monitoring of structures and measuring strain and temperature are provided. The transmission-type extrinsic Fabry-Perot interferometric optical fiber sensor includes first single-mode optical fiber and second single-mode optical fiber, laser device, and optical detector. The first single-mode optical fiber is inserted into an end of a capillary quartz-glass tube and the second single-mode optical fiber is inserted into the other end of the capillary quartz-glass tube. Air gap is formed between the first single-mode optical fiber and the second single-mode optical fiber in the capillary quartz-glass tube. Gap length of the air gap changes in response to magnitude and direction of transformation of the capillary quartz-glass tube. The laser device launches light into an end of the first single-mode optical fiber.

Abstract: Numerous features may be incorporated into a wavelength locker to reduce the noise inherent therein. These features may be used in any combination thereof. These features include avoiding the use of reflectors, using a diffractive splitter which outputs evanescent beams for diffractive orders greater than one, using anti-reflective coatings, using an opaque material with through holes for the light, and designing the wavelength locker to be used at a tilt.

Abstract: A multireflector fiber optic filter apparatus, wherein the transmittance and reflectance spectra are periodic in frequency, the apparatus comprising an etalon with N equally spaced reflectors wherein the transmittance and reflectance spectra of said etalon are periodic in optical frequency with a period given by the formula: &Dgr;&ngr;FSR=c/(2ngL), where c=the free space speed of light; ng=the group refractive index for the light propagating in the medium between the reflectors, L=separation between said reflectors, and N is an integer=3,4,5, . . . In a further aspect, an optical circulator is connected to the etalon and an optical fiber is connected to the optical circulator for reflected output.

Abstract: In a method for influencing and measuring pulsed electromagnetic illumination, e.g. parallel laser light (L), said illumination or light can be spatially divided, in particular, in an autocorrelator comprising a beam receptor (12), can be recombined behind said beam receptor by a superposition or focusing device (18 or 58) and can be detected in the recombinant area by a detector (20). As the transmission system (52), the beam receptor comprises beam profile dividers in a penetrable housing (50), in the form of at least two transmission parts (54; 56), with or in which separate, preferably parallel component beams (S, T) can be modified in their time-based beam characteristics, before being recombined.

Abstract: A wavelength reference device for tuning a tunable Fabry-Perot filter and/or a tunable VCSEL to a desired frequency, where the device uses a modified Michelson interferometer to generate a series of reference frequencies

Abstract: A miniaturized chemical sensor features an optical microcavity coated with a surface layer, and a waveguide that evanescently couples light into the microcavity. The surface layer is adapted to chemically interact with one or more molecule species in a chemical vapor surrounding the microcavity, so as to alter the evanescent light coupling between the optical microcavity and the waveguide. The chemical interaction causes a change in the index of refraction of the microcavity, resulting in a measurable phase difference readout. The refractive index sensitivity is substantially increased, because of the high Q-value of the optical microcavity.

Abstract: There are disclosed a wavelength monitoring device of tunable laser sources and a method thereof. A Fabry-Perot etalon is provided to detect the wavelength drift, and furthermore, a Fabry-Perot laser diode or a light emitting diode is provided to recognize the channel of the wavelength. The wavelength drift is used to determine the junction voltage of each corresponding channel in advance. Then, the actually detected junction voltage of the diode is used to determine the channel of the wavelength, thereby accurately detecting the actual channel wavelength.

Abstract: An optical measurement and inspection method and apparatus having enhanced path length detection uses a Fabry-Perot cavity to increase the phase detection sensitivity for light reflected from optical structures within a device under inspection. A partially reflective surface is inserted between an illumination subsystem and the device under inspection and the position of the partially reflective surface may be adjusted by a positioner to create the Fabry-Perot cavity between one or more surfaces within the device under inspection. The detection of phase changes is improved, providing improved sensitivity to optical path differences produced by structures within the device under inspection.

Abstract: A process for tunable filter train alignment comprises detecting a spectral response of the filter train and aligning an optical fiber that transmits an input optical signal to the filter train during operation. Further, the tunable filter is moved relative to the filter train in response to a spectral response of the filter train. As a result, the alignment and spectral response of the tunable filter train are optimized. In the preferred embodiment, the alignment and SMSR optimization occur simultaneously with respect to each other.

Abstract: An integrated wavelength monitor and a method for obtaining such a device are disclosed. The device suitable for integration into a laser semiconductor laser module for fiber optic communication can be made in the following way: An interference filter is created directly onto a position sensitive photo detector by depositing a number of layers of different optical transparent materials forming an optical filter. The interference filter may also be created separately and subsequently mounted directly on top of the detector. The integrated position sensitive device (13) is mounted with an angle behind a laser in the same position as a normal power monitor detector. The electrically derived lateral position of light hitting the Position Sensitive Device provided with the interference filter will be dependent of the wavelength of the incident light and this derived position is used for the wavelength monitoring.

Abstract: An electrically variable optical filter includes a first optical element including a first angled face and a second optical element including a second angled face. The second angled face is substantially parallel to and spaced apart from the first angled face. At least one separation actuator is affixed between the first optical element and the second optical element and is operable to change a separation distance D between the first angled face and the second angled face. Light waves transmitted through the first optical element are selectively transmitted through to or reflected away from the second optical element as a function of wavelength and the separation distance D.

Abstract: A process for tunable filter train alignment comprises detecting a spectral response of the filter train and aligning an optical fiber that transmits an input optical signal to the filter train during operation. Further, the tunable filter is moved relative to the filter train in response to a spectral response of the filter train. As a result, the alignment and spectral response of the tunable filter train are optimized. In the preferred embodiment, the alignment and SMSR optimization occur simultaneously with respect to each other.

Abstract: Within a Fabry-Perot filter apparatus, a method for fabricating the Fabry-Perot filter apparatus and a method for operating the Fabry-Perot filter apparatus, there is employed a Fabry-Perot filter and at least one color filter layer, both assembled over a substrate and covering at least two optical transducer elements which are formed within the substrate. Within the foregoing apparatus and methods, the at least one color filter layer comprises at least two color filter elements of separate color, each registered with a separate optical transducer element within the at least two optical transducer elements. The apparatus and methods provide for enhanced optical discrimination properties.