Abstract: A heterodyne optical network analyzer and method for device characterization reduces the effect of relative intensity noise (RIN) in interferometric optical measurements by subtracting the measured intensities of first and second interference signals derived from an optical interferometer. The first and second interference signals are produced by combining a first lightwave transmitted to an optical device being characterized with a second lightwave, which is a delayed version of the first lightwave. The first and second lightwaves are derived by splitting an input lightwave having a continuously swept optical frequency generated by a light source, such as a continuously tunable laser.

Abstract: Optical systems for selectively altering the propagation of light are provided. A representative optical system incorporates an optical device that includes a first para-electric holographic medium. The first para-electric holographic medium stores a first hologram that can exhibit a first active mode. The first hologram exhibits the first active mode when a first electric field is applied to the first para-electric holographic medium. When in the first active mode, the first hologram directs light incident upon the first holographic medium to a first location. Methods and other systems also are provided.

Abstract: An optical heterodyne detection system includes an input signal and a local oscillator signal that are combined in an optical coupler and output as a first beam and a second beam. A polarizing beam splitter is optically connected to the optical coupler in order to receive the first beam and the second beam. The polarizing beam splitter includes four outputs for outputting four beams to four photodetectors including two polarized portions of the first beam and two polarized portions of the second beam. The four photodetectors generate four electrical signals in response to respective ones of the four beams. The four electrical signals are transmitted to a processor and processed to provide an output response that is independent of the polarization state of the original input signal and in which the intensity noise has been suppressed.

Abstract: A filter for generating an output light signal having one or more output spectral lines selected from a plurality of potential spectral lines contained in an input light signal. The filter includes a channel filter for filtering the input light signal to create a notched light signal having a spectrum devoid of light at a first wavelength. The filter also includes a variable wavelength reflector for reflecting light having a wavelength equal to a reflection wavelength, the reflection wavelength being selectable from the first wavelength and a second wavelength equal to the wavelength of one of the spectral lines. The output of the channel filter is coupled to the input of the variable wavelength reflector. The output of the variable wavelength reflector includes the output light signal. The channel filter can be constructed using a number of known optical components such as fiber Bragg reflectors, array waveguide filters, Mach Zehnder filters, or absorption filters.

Abstract: Heterodyne based optical spectrum analysis (OSA) involves mixing an input signal with a swept local oscillator signal to generate a heterodyne beat signal and then stretching the heterodyne beat signal before the signal is sampled. A system for optical spectrum analysis includes a local oscillator source, an optical coupler, a heterodyne receiver, and a processor. A circuit for stretching the heterodyne beat signal is included in the heterodyne receiver and may include a diode in series with a capacitor and a resistor or a diode in series with a capacitor and a switch. Stretching the heterodyne beat signal involves extending the duration of the signal so that the signal can be detected with fewer samples per unit of time than an unstretched signal. Another embodiment of an OSA includes a first data acquisition unit for obtaining low resolution data and a second data acquisition unit for obtaining high resolution data.

Abstract: A tunable optical cavity constructed from a fixed mirror and a movable mirror is disclosed. A circuit applies an electrical potential between first and second electrically conducting surfaces thereby adjusting the distance between the fixed and movable mirrors. The fixed mirror and the moveable mirror are positioned such that the mirrors form the opposite ends of the optical cavity. The distance between the fixed mirror and the moveable mirror is a function of the applied electrical potential. The thermally induced vibrations are reduced by utilizing an electrical feedback circuit that measures the distance between the mirrors. The feedback circuit dynamically changes the potential between the substrate and the support member so as to reduce fluctuations in the cavity resonance frequency.

Abstract: An optical heterodyne detection system includes an optical pre-selector that has an adjustable passband which is adjusted to track the wavelength of a swept local oscillator signal. In an embodiment, an input signal is combined with a swept local oscillator signal and the combined optical signal is filtered by the optical pre-selector. In another embodiment, the input signal is filtered by the optical pre-selector before the input signal and the swept local oscillator signal are combined. Filtering the input signal or the combined input signal and the swept local oscillator signal to pass a wavelength band that tracks the wavelength of the swept local oscillator signal reduces the noise contributed from WDM signals and increases the dynamic range of the optical heterodyne detection system. An embodiment of the optical heterodyne detection system includes an optical combining unit, an optical pre-selector for the combined input and swept local oscillator signals, and a photodetector.

Abstract: A coherent optical spectrum analyzer is provided in which an optical balancing tone having a specific signature is injected into a signal path of a balanced optical receiver. A measuring unit is provided to analyze the balancing tone component in the signal output from the balanced optical receiver and determine characteristics of the optical receiver. A compensation unit is provided for providing compensation to counter, or negate any imbalances determined via the measuring unit. The balanced optical receiver is preferably a polarization state independent optical receiver.

Abstract: An optical detection system includes a planar waveguide optical coupler that is directly adjacent to a polarizing beam splitter. The planar waveguide optical coupler combines an input signal with a local oscillator signal and the polarizing beam splitter divides the combined optical signal into orthogonally polarized beams. The orthogonally polarized beams are detected by first and second optical detectors. In one embodiment, the planar waveguide optical coupler is in contact with the polarizing beam splitter, in another embodiment, the planar waveguide optical coupler is attached to the polarizing beam splitter, and in another embodiment, the planar waveguide optical coupler and the polarizing beam splitter are attached to opposite sides of a polarization rotator.

Abstract: Heterodyne-based optical spectrum analysis involves filtering a heterodyne beat signal with at least one matched filter in order to improve the signal-to-noise ratio and the spectral resolution of the heterodyne-based optical spectrum analysis. In an embodiment, an input signal is combined with a swept local oscillator signal in an optical coupler. The combined optical signal is output to a receiver and a heterodyne beat signal is detected. The heterodyne beat signal is filtered by a matched filter unit and the filtered heterodyne beat signal is utilized to generate an output signal that is indicative of an optical parameter of the input signal. By utilizing the quadratic phase behavior of the heterodyne beat signal in signal processing, the resolution of a heterodyne-based OSA can be substantially improved over known heterodyne-based OSAs.

Abstract: A system and method for measuring the group delay of an optical device under test (DUT) utilizes an optical frequency counter in conjunction with a test interferometer to compensate for the non-uniform frequency changes of an input optical signal used by the test interferometer to measure the group delay. The group delay of the optical DUT is measured using the zero-crossings of an AC coupled heterodyne beat signal produced by the test interferometer from the input optical signal. In the measurement of the group delay, phase changes in the heterodyne beat signal caused by the non-uniform frequency changes of the input optical signal are compensated by using the measured optical frequency of the input optical signal. The optical frequency is detected by the optical frequency counter. The detected optical frequency is indicative of the non-uniform frequency changes of the input optical signal.

Abstract: A method and a system for monitoring specific channels in a WDM system involve splitting a WDM signal into multiple parallel signals, filtering the parallel signals with corresponding individually tunable filters in order to pass specific channels to each filter, and then detecting the presence of passed channels with dedicated detectors that correspond to the tunable filters. In a preferred embodiment, the initial WDM signal is demultiplexed by wavelength into multiple different transmission groups and each filter can be individually tuned over a channel range that corresponds to the range of channels within the transmission group that is directed to the filter. The preferred individually tunable filters are vertical cavity filters formed utilizing semiconductor wafer processing techniques, and the preferred photodetectors are simple low cost single-cell photodetectors.

Abstract: A system and method for measuring the group delay of an optical device under test (DUT) utilizes an optical frequency counter in conjunction with a test interferometer to compensate for the non-uniform frequency changes of an input optical signal used by the test interferometer to measure the group delay. The group delay of the optical DUT is measured using the zero-crossings of an AC coupled heterodyne beat signal produced by the test interferometer from the input optical signal. In the measurement of the group delay, phase changes in the heterodyne beat signal caused by the non-uniform frequency changes of the input optical signal are compensated by using the measured optical frequency of the input optical signal. The optical frequency is detected by the optical frequency counter. The detected optical frequency is indicative of the non-uniform frequency changes of the input optical signal.

Abstract: Heterodyne-based optical spectrum analysis involves filtering a heterodyne beat signal with at least one matched filter in order to improve the signal-to-noise ratio and the spectral resolution of the heterodyne-based optical spectrum analysis. In an embodiment, an input signal is combined with a swept local oscillator signal in an optical coupler. The combined optical signal is output to a receiver and a heterodyne beat signal is detected. The heterodyne beat signal is filtered by a matched filter unit and the filtered heterodyne beat signal is utilized to generate an output signal that is indicative of an optical parameter of the input signal. By utilizing the quadratic phase behavior of the heterodyne beat signal in signal processing, the resolution of a heterodyne-based OSA can be substantially improved over known heterodyne-based OSAs.

Abstract: Heterodyne-based optical spectrum analysis involves measuring the sweep rate of a swept local oscillator signal and then generating an output signal that accounts for non-uniformities in the sweep rate of the swept local oscillator signal. In an embodiment, an input signal is combined with a swept local oscillator signal in an optical coupler and the sweep rate of the swept local oscillator signal is measured in a relative frequency measurement system. The combined optical signal is output from the optical coupler to a receiver and a heterodyne beat signal is generated. The heterodyne beat signal and measured local oscillator frequency sweep rate information are utilized by a signal processor to generate an output signal that is indicative of an optical parameter of the input signal and that accounts for non-uniformities in the sweep rate of the local oscillator signal.

Abstract: Bistable switchable waveguide includes a guide layer constructed from a layer having a first index of refraction when the molecules of the material are aligned in a first direction and a second index of refraction when the molecules are aligned in a direction orthogonal to the first direction. The guide layer is sandwiched between first and second surfaces that are in contact. The first surface causes the molecules of the guide layer adjacent to it to be aligned in the first direction. The second surface also includes a third region in which the second surface causes the molecules of the guide layer adjacent to it to be aligned in a second direction. The waveguide has first and second electrodes for causing the molecules of the guide layer to be aligned in a second direction that is the second direction in a region bounded by the third region and first surface.

Abstract: A coherent optical spectrum analyzer is provided in which an optical balancing tone having a specific signature is injected into a signal path of a balanced optical receiver. A measuring unit is provided to analyze the balancing tone component in the signal output from the balanced optical receiver and determine characteristics of the optical receiver. A compensation unit is provided for providing compensation to counter, or negate any imbalances determined via the measuring unit. The balanced optical receiver is preferably a polarization state independent optical receiver.

Abstract: A method and an apparatus for determination of properties, e.g. of elements of the Jones matrix of an optical device under test, comprising the steps of: producing an incoming light beam, splitting the light beam into a first light beam and a second light beam, coupling the first light beam, preferably having two parts delayed with respect to each other, with a given initial polarization into the optical device under test, letting the second light beam travel a different path than the first light beam, superimposing the first light beam and the second light beam to produce interference between the first light beam and the second light beam in a resulting superimposed light beam, splitting the superimposed light beam into a third light beam polarization dependent and a fourth light beam, detecting the power of the third and the fourth light beam as a function of frequency when tuning the frequency of the incoming light beam over a given frequency range, deriving optical properties, e.g.

Abstract: A bistable switchable waveguide having first and second states. The waveguide guides light along a predetermined path in the first state while providing no guiding of the light in the second state. The waveguide includes a guide layer constructed from a layer of a material having a first index of refraction when the molecules of the material are aligned in a first direction and a second index of refraction when the molecules are aligned in a direction orthogonal to the first direction. The guide layer is sandwiched between the first and second surfaces that are in contact with the guide layer. The first surface causes the molecules of the guide layer adjacent to the first surface to be aligned in the first direction. The second surface has first and second regions in which the second surface causes the molecules of the guide layer adjacent to the second surface to be aligned in the first direction.

Abstract: A polarity-independent optical receiver is constructed so that the bias voltage applied to the optical receiver may be applied in a polarity-independent manner. The polarity-independent optical receiver is also constructed in a balanced arrangement, thus providing the ability to effectively suppress common-mode intensity noise present at the optical receiver. The polarity-independent optical receiver may advantageously be fabricated using metal-semiconductor-metal (MSM) technology.