Abstract: An extendable four-port circulator includes a middle birefringent crystal, a first birefringent crystal, a first non-reciprocal device, a second birefringent crystal, and a second non-reciprocal device. The first non-reciprocal device is coupled to the first birefringent crystal. The second non-reciprocal device is coupled to the second birefringent crystal. The middle birefringent crystal includes a first surface, a second surface, a third surface, and a fourth surface. The first surface is coupled to the first non-reciprocal device. The second surface is coupled to the second non-reciprocal device. The third surface defines first and second extension interfaces. The fourth surface defines third and fourth extension interfaces. A multi-port circulator includes at least one extendable four-port circulator.

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: This invention discloses an optical interleaver that includes a first collimating lens for collimating an input optical signal into collimated beams and a second collimating lens for focusing the collimated parallel beams into an output optical fiber. The interleaver further includes a phase delay difference generating means for generating a phase-delay difference between portions of the collimated parallel beams for generating an interference in the second collimating lens for selectively enhance signal transmission of certain wavelengths. In a preferred embodiment, the phase delay difference generating means comprising a glass plate blocking a portion of the collimated parallel beams for generating a phase delay for a portion of the collimated parallel beams passing therethrough. In another preferred embodiment, the phase delay difference generating means comprising a glass plate having an upper portion covering an upper portion of the collimated parallel beams.

Abstract: In another aspect, the invention provides a closed loop optical circulator including a first crystal for splitting an input light signal into two components, a second crystal for deflecting the two components received from the first crystal in a direction if the two components have a first polarization, a third crystal for deflecting the two components received from the second crystal in an opposite direction if the two components have the first polarization, and a fourth crystal for joining the two components received from the third crystal.

Abstract: An extendable four-port circulator includes a middle birefringent crystal, a first birefringent crystal, a first non-reciprocal device, a second birefringent crystal, and a second non-reciprocal device. The first non-reciprocal device is coupled to the first birefringent crystal. The second non-reciprocal device is coupled to the second birefringent crystal. The middle birefringent crystal includes a first surface, a second surface, a third surface, and a fourth surface. The first surface is coupled to the first non-reciprocal device. The second surface is coupled to the second non-reciprocal device. The third surface defines first and second extension interfaces. The fourth surface defines third and fourth extension interfaces. A multi-port circulator includes at least one extendable four-port circulator.

Abstract: A four-port loop optical circulator includes a first, a second, a third and a fourth optical ports for receiving optical beam therein. The circulator further includes a plurality of optical components. The optical components include a walk-off crystal for generating a vertical optical path displacement for a vertical polarized optical beam and for passing a horizontally polarized optical beam therethrough maintaining a same optical path. The optical components also include a vertical displacement device for shifting an optical path along a vertical direction with a predefined vertical displacement for an optical beam transmitted with a particular polarization. The vertical displacement device is coupled to the walk-off crystal for guiding a beam received from the fourth port to project from the first port.

Abstract: This invention discloses an optical collimator that includes a built-in tap-out projection optical arrangement for projecting a portion of an incoming beam to a tap-out beam-transmission fiber. In one of the preferred embodiments, the built-in tap-out projection optical arrangement further includes a front surface having an incline angle for projecting a portion of an incoming beam to a tap-out beam transmission fiber. In another preferred embodiment, the built-in tap-out projection optical arrangement further includes a prism having a pair of inclined front surfaces for projecting the incoming beam into an output beam and a tap out beam. In yet another preferred embodiment, the built-in tap-out projection optical arrangement further includes a partially reflective front surface and a reflective mirror projecting the incoming beam into an output beam and a tap out beam.

Abstract: This invention discloses a method for detecting a leak from a sealed optical device. The method includes steps of: A) injecting a target gas with no performance interference to the sealed optical device for leak detection followed by sealing the sealed optical device. B) placing the sealed device in a leak testing chamber and measuring a background level of the target gas in the leak testing chamber. C) heating the sealed device to a gas-expelling temperature for expelling the target gas from the leak in the sealed optical device. And, D) detecting the target gas in a one-part-per million (PPM) range in the leak-detecting chamber for an comparing with the background level of the target gas for determining the leak in the sealed optical device.

Abstract: A wavelength slicing apparatus and method includes two filters having passbands offset from each other and from a signal channel. The offset passbands enhance transmission where they overlap and reduce transmission where they do not overlap such that transmission of optical signals in a neighboring channel is suppressed. A third filter having a passband centered on the signal channel frequency may be included to enhance optical signal isolation. Wavelength slicing techniques may be used for channel isolation or passband flattening. Wavelength slicing can be incorporated into wavelength division multiplexing (WDM) optical switching to improve optical isolation between channels during routing, multiplexing and demultiplexing operations.

Abstract: A wavelength division multiplexing (WDM) apparatus and a WDM method are disclosed. The apparatus generally comprises an optical interleaver coupled to one or more WDM modules. Two or more interleaver modules may be cascaded together to expand the channel handling capacity. Alternatively, two or more WDM modules may be cascaded together to divide the even and odd channels into subsets. The interleaver interleaves a first signal, containing one or more odd channels and one or more even channels with a second signal, containing a portion of the odd channels and a third signal containing a portion of the even channels. A characteristic frequency spacing between adjacent even channels in the second signal and/or a characteristic spacing between adjacent odd channels in the third signal is about two or more times the value of a characteristic frequency spacing of adjacent channels in the first signal.

Abstract: This invention discloses an optical collimator that includes a built-in tap-out projection optical arrangement for projecting a portion of an incoming beam to a tap-out beam-transmission fiber. In one of the preferred embodiments, the built-in tap-out projection optical arrangement further includes a front surface having an incline angle for projecting a portion of an incoming beam to a tap-out beam transmission fiber. In another preferred embodiment, the built-in tap-out projection optical arrangement further includes a prism having a pair of inclined front surfaces for projecting the incoming beam into an output beam and a tap out beam. In yet another preferred embodiment, the built-in tap-out projection optical arrangement further includes a partially reflective front surface and a reflective mirror projecting the incoming beam into an output beam and a tap out beam.

Abstract: A deinterleaver includes three polarization interferometers and a dispersion compensator, the input light beam containing all channels passing through the dispersion compensator and the first polarization interferometer, the light beam being separated by a polarization beam splitter into an even channel beam and an odd channel beam with the even channel beam passing through a second polarization interferometer and the odd channel beam passing through a third polarization interferometer. A dispersion compensated deinterleaver as above in which all three polarization interferometers have pass bands corresponding to all channels and in which there are two output ports. A dispersion compensated deinterleaver in which the first polarization interferometer has pass bands for all channels, the second polarization interferometer has pass bands for even channels, the third polarization interferometer has pass bands for odd channels and in which there are four output ports.

Abstract: A tunable optical fiber grating package with a supporting assembly and an optical fiber portion having at least one grating between a first end and a second end of the fiber portion is provided. The first end and the second end of the fiber portion define a longitudinal direction and the at least one grating has an optical characteristic that varies with strain of the fiber portion. The supporting assembly has a first supporting member formed of a material having ultra low CTE, a second supporting member formed of a material having a negative CTE and a tuning means for changing the dimension of the first supporting member substantially along the longitudinal direction. The first supporting member and the second supporting member are bonded together.

Abstract: An optical channel monitor (OCM) or filter for analyzing an incident light carrying a number of narrow band signal channels such as WDM or DWDM channels. The OCM or filter use an acousto-optic tunable filter to receive and refract from an incident light a refracted light such that the refracted light contains a test channel with a center frequency &ngr;0. A first birefringent element is provided for filtering from the refracted light a first polarized light and a second polarized light orthogonal to the first polarized light. The transmission curves are engineered such that the transmissions of the first and second polarized light are substantially equal at the center frequency &ngr;0 of the test channel. The OCM or filter has a second birefringent element for filtering from the first polarized light a first polarized portion and a second polarized portion.

Abstract: An optical de-interleaver for de-interleaving light beams of odd and even channel signals having channel spacing S into light beams of odd channel signals having channel spacing 2S and light beams of even channel signals having channel spacing 2S is provided which has only one polarization interferometer and one optical dispersion compersator. A 50/100 GHz de-interleaver and a 50/200 GHz de-interleaver with high isolation and dispersion compensation are provided by applying this unique arrangement. The optical de-interleaver has a 0.5 dB passband width of about 30 GHz and a −25 dB isolation stopband width of about 30 GHz.

Abstract: A method of fabricating multiple superimposed Bragg gratings in the core of a portion of a photosensitive fiber is provided where only one common phase-mask is used. The multiple superimposed Bragg gratings are inscribed in the portion of the photosensitive fiber by applying different predetermined longitudinal stresses to the portion for each corresponding writing. The different predetermined longitudinal stresses are applied to the portion of the photosensitive fiber by stretching the portion along its longitudinal axis bi-directionally and simultaneously such that the centers of all fiber Bragg gratings imprinted in the portion are substantially superimposed at the center of the portion of the photosensitive fiber.

Abstract: This invention discloses a machine for automatically attaching an optical filter to a lens. The machine includes lens table for supporting the lens. The machine further includes an attachment-medium dispenser system for dispensing a plurality of gapped-dots of an attachment-medium on a top surface of the lens along a peripheral line substantially according to a bottom-surface shape of the filter. The machine further includes a surface-mounting system for mounting the optical filter onto the top surface of the lens for stamping the gapped-dots into a continuous peripheral attachment-seal for attaching the filter to the lens and for sealing a peripheral interface-edge between the filter and the lens.

Abstract: An etalon includes a tuning plate in the air-gap between the etalon mirrors. The method of tuning includes selecting a tuning plate that makes the optical length of the etalon slightly less than required for ITU and then rotating the tuning plate through a small angle until tuning is complete. The tuning plate material is selected to provide dispersion compensation and to compensate for thermal expansion of the mirror spacers.

Abstract: The present invention provides an optical dispersion compensator with relatively small size and low insertion loss comprising a Fabry-Perot etalon and a dual-fiber collimator having a dual-fiber pigtail and a GRIN lens. The dual-fiber pigtail has an input fiber and an output fiber. An optical signal is coupled into the input fiber and then collimated by the GRIN lens into a collimated incident beam that is incident on the Fabry-Perot etalon with an incident angle. The collimated incident beam is reflected back by the Fabry-Perot etalon into a collimated reflected beam that is collected by the GRIN lens and coupled into the output fiber. By adjusting the separation between the input fiber and the output fiber of the dual-fiber pigtail, the collimated incident beam will change its incident angle and reflected angle. By tuning this angle, the group delay pattern of the output optical signal through the output fiber will shift along with wavelength, therefore dispersion compensation can be achieved.

Abstract: This invention presents a novel tunable module that can be incorporated in various optical devices, to provide a tunability and selectivity in a characteristic of an optical signal by effectively modifying its optical path lengths. The present invention also provides an optical isolator that incorporates such a tunable module, so that polarization mode dispersion is minimized to an arbitrarily low level. The present invention further describes methods for incorporating the tunable module in optical devices and for tuning the optical characteristics.