The present invention provides a dense wavelength division multiplexer for separating an optical signal into optical channels. It includes at least one birefringent plate, and a polarization beam splitter optically coupled to the at least one birefringent plate, the polarization beam splitter and at least one birefringent plate for separating one or more of the plurality of optical channels by introducing a phase difference between at least two of the plurality of optical channels, where the sep...

According to the present invention, a multi-window wavelength division multiplexer (MWDM) is coupled to a correcting filter characterized by a shallow modulation depth and a channel separation smaller than the MWDM. A correcting filter is coupled to an input of the MWDM or to each of the two outputs of the MWDM. By changing the modulation depth and/or channel separation of the correcting filter(s), the spectral response of the filter can be adjusted to produce a more uniform gain (i.e., a "flat-...

Optical logic gates are constructed from Mach-Zehnder Interferometer (MZI) optical circuits. A multi-mode interference (MMI) splitter divides a continuous-wave input into two branches of the interferometer. Each branch has a semiconductor optical amplifier (SOA). When a logic input having a logic-high power level is applied to one of the SOA's, cross-phase modulation occurs in the SOA. The phase shift increases through the SOA. The branch coupled to the logic input has a relative phase shift of ...

A distributed fiber-grating-based sensing system, the system comprises one or more scanned birefringence fiber interferometers to detect the small wavelength shift of the light reflected from the fiber grating, a wavelength demultiplexer to separate the lights from each fiber grating, a reference fiber grating for determining the absolute optical wavelengths. Compared with the prior art, the system has advantages of easier fabrication, better stabilization, and can be customized for different ap...

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 collimato...

A method for determination of/compensation for the bias/random walk errors induced by the light source in fiber-optic Sagnac interferometers employing a modulation method for stochastically independent shifting of the operating point to the points of highest sensitivity. A reference beam is output from the light beam emitted from the light source of the interferometer and passed to the fiber coil to produce a proportional reference intensity signal. Such signal is demodulated with the demodulati...

An apparatus including a stage configured to be moved. A first laser interferometer measures a position of the stage in a first direction. A second laser interferometer measures a position of the stage in the first direction. A control unit (i) obtains a position of the stage based on an output of one of the first and second laser interferometers, (ii) controls a position of the stage based on the obtained position of the stage, (iii) performs switching of one of the first and second laser inter...

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 collimato...

An optical device includes: a first polarization beam splitter (PBS); a first set of optical rotators optically coupled to the first PBS; a second PBS optically coupled to the first set of optical rotators; a first reflection interferometer (RI) optically coupled to the second PBS; a second RI optically coupled to the first PBS; a second set of optical rotators optically coupled to the second PBS; a third PBS optically coupled to the second set of optical rotators; and a third RI optically coupl...