Abstract: An optical device includes a walk-off plate, a lens, a half wave plate, a reflective device, and a non-reciprocal device. The walk-off plate is adapted for coupling to a first port and a second port. The half wave plate is positioned between the walk-off plate and the lens. The half wave plate is also configured to change the polarization of the light received from the first port by a first angle. The non-reciprocal device is positioned between the lens and the reflective device, and the non-reciprocal device is also configured to rotate light passing therethrough by a second angle.

Abstract: A variable optical attenuator includes a first lens, a MEMS device, a second lens, and a wedge. The first lens is configured to collimate an input light received on a first port and focus an output light on a focus point proximate to a second port. The MEMS device includes a reflection surface having a tilting angle thereof controllable by a control variable. The second lens has a focus point positioned proximate to the reflection surface of the MEMS device. The wedge is positioned between the first lens and the second lens and is configured to refract the input light received from the first lens to enter the second lens and refract the output light received from the second lens to enter the first lens.

Abstract: An optical system provides reflection-type isolation, and may include variable optical attenuation and/or a tap monitor. The optical system may include an optical isolator with a beam splitter such as a walk-off plate, a focusing element such as a GRIN lens, a combiner comprising two birefringent wedges and a non-reciprocal rotating device such as a Faraday rotator, a compensation device, and a reflector. The Faraday rotator may be variable to provide variable attenuation. The reflector may be a partial reflector to provide a tap monitor. The optical system is configured so that light transmitted into the optical isolator through the input fiber may be transmitted out of the optical isolator through the output fiber, but light transmitted into the optical isolator through the output fiber is generally not transmitted out of the optical isolator through the input fiber.

Abstract: A wavelength division multiplexer includes a filter, a first lens, a second lens, a first holder, and a second holder. The pass-band of the filter is dependent on the incident angle of light incident upon the filter. The first lens is positioned on a first side of the filter. The second lens is positioned on a second side of the filter. The first holder is configured to hold at least first, second, third, and fourth fibers proximate to the first lens. The first holder is also configured to hold a center of the second and the fourth fibers on opposite sides of a line connecting a center of the first and the third fibers. The second holder is configured to hold at least fifth and sixth fibers proximate to the second lens.

Abstract: A three-port circulator includes a non-reciprocal rotating element, a first birefringent wedge, and a second birefringent wedge. The non-reciprocal rotating element has a rotation axis and rotates the polarization of light passing through it by an predetermined angle. The first birefringent wedge has a first optical axis substantially perpendicular to the rotation axis. The second birefringent wedge has a second optical axis substantially perpendicular to both the rotation axis and the first optical axis. The second birefringent wedge is optically coupled between the non-reciprocal rotating element and the first birefringent wedge.

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: 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.

Abstract: A polarization splitter and combiner for processing a beam containing a first polarization and a second polarization to spatially separate these polarizations by using a birefringent element for receiving the beam and walking off the first polarization from the second polarization by an initial walk-off distance. A first lensing element with an optical axis is oriented to admit the first polarization at a first input point and output the first polarization at a first output angle to the optical axis and the second polarization at a second output angle to the optical axis. A second lensing element positioned after the first lensing element is oriented to receive the polarizations at input angles equal to their respective output angles, and outputs both polarizations at a first and second output point respectively. In a symmetrical arrangement, the first and second output points are separated by the initial walk-off distance.

Abstract: This invention provides a novel wavelength filter module that reduces the number of components required in an optical interleaver, and can be configured in various ways suitable for practical applications. An optical interleaver of the present invention incorporating such a wavelength filter module is simpler and more compact in design, lower in insertion losses, polarization dependent loss (PDL) and cost, while more reliable in performance. The optical interleaver of the present invention can be advantageously configured as a multiplexer, de-multiplexer, or a router.

Abstract: The present invention provides a line of optical interleavers in which a novel beam-swapping element is utilized. The beam-swapping element of the present invention provides an effective and inexpensive alternative to polarization rotators and birefrigent elements employed in the prior art optical interleavers, hence rendering a simple and low-cost assembly to the optical interleavers of the present invention. The optical interleavers of the present invention further advantageously exploit a combination of two wavelength filters to cancel out wavelength-filter-induced-dispersion. Efforts are also painstakingly made in the optical interleavers of the present invention to substantially minimize other dispersion effects. As such, the optical interleavers of the present invention constitute the first kind in the art in which various dispersion effects are substantially minimized. Such characteristics would be highly desirable in fiber-optic networks.

Abstract: A method and system for providing a splitter/combiner is disclosed. The splitter/combiner includes a first birefringent wedge having a first optic axis and a first wedge angle and a second birefringent wedge having a second optic axis and a second wedge angle. The second birefringent wedge is optically coupled with the first birefringent wedge. The second wedge angle is complementary to the first wedge angle. The second optic axis is perpendicular to the first optic axis such that an extraordinary signal for the first birefringent wedge is an ordinary signal for the second birefringent wedge. The first and second birefringent wedges establish a first path for a first portion of a first optical signal and establish a second path for a second portion of the first optical signal. The first path and the second path are separated by an angle. The first optical signal travels from the first birefringent wedge to the second birefringent wedge.

Abstract: A method and system for providing an optical filter is disclosed. The method and system include providing a first fiber for carrying a first optical signal and a second fiber for carrying a second optical signal. The first fiber has an end. The method and system also include providing a filter and a lens disposed between the filter and the end of the first fiber. The filter has a surface and is for filtering the first optical signal to provide the second optical signal. The lens has an axis and is for collimating the first optical signal. A normal to the surface of the filter is disposed at a first nonzero angle to the axis. The first optical signal has a first direction of propagation at the surface of the filter. The first direction of propagation is disposed at a second nonzero angle from the normal to the surface of the filter. The filter can be tuned by rotating the filter around the axis. Furthermore, additional fibers can be added to simultaneously filter multiple channels.

Abstract: An optical interleaver having a deflection plate disposed along an optical path between two input/output ports. The interleaver generally comprises a first birefringent element optically coupled to at least two of the input/output ports, first and second polarization rotators, a wavelength filter, and a second birefringent element. The interleaver may be configured to operate as a multiplexer, a de-multiplexer, or a router. The interleaver may further comprise a collimator that couples two or more different optical signals to one of two or more optical fibers. A preferred embodiment includes a reflector that reflector reflects an optical signal back through the elements of the interleaver in reverse order to the input/output ports. This configuration reduces the number of components required for the interleaver and allows the use of shorter birefringent elements.

Abstract: A mechanical optical switch with a first port for holding a first optical fiber and a second port for holding a second optical fiber and a lensing element positioned in front of the first and second ports. The switch has a signal port holding a signal or input fiber which emits a light beam to be switched between the first and second fibers. The light beam propagates along a free beam path to the first lensing element and is in-coupled into the first optical fiber. The switch is equipped with a beam guiding element, such as a wedge, which can be moved in and out of the free beam path for directing the light beam to the second fiber. The wedge is designed to shift the light beam by an offset and rotate it by an angle.

Abstract: An optical interleaver having a reflector that reflects an optical signal from one or more input/output ports back through the elements of the interleaver in reverse order to the input/output ports. The interleaver generally comprises a first birefringent element optically coupled to at least three input/output ports, first and second polarization rotators, a wavelength filter, a second birefringent element and the reflector. The interleaver may further comprise a compensation plate that compensates for phase differences due to different optical path lengths for ordinary and extraordinary rays in one of the birefringent elements. This configuration reduces the number of components required for the interleaver and allows the use of shorter birefringent elements. The interleaver may be configured to operate as a multiplexer, a de-multiplexer, or a router.

Abstract: A system and method for filtering are disclosed. The system and method include providing first, second, third and fourth fibers for carrying a first, second, third, and fourth optical signals, respectively. The method and system also include providing a holder, a filter, and a first wedge assembly. The holder is for receiving the first fiber, the second fiber, the third fiber, and the fourth fiber therein. The filter is for filtering the first optical signal, the second optical signal, the third optical signal, and the fourth optical signal to provide a first filtered optical signal, a second filtered optical signal, a third filtered optical signal, and a fourth filtered optical signal. The first wedge assembly is disposed between the holder and the filter.

Abstract: A method and system for providing an optical circulator is disclosed. The optical circulator includes a first port, a second port, a third port, and means for establishing a first optical path and a second optical path. The first optical path is from the first port to the second port. The second optical path is from the second port to the third port. The optical path establishing means also includes a wedge and a first birefringent material. The wedge intersects the second optical path but not the first optical path. The wedge is for ensuring that the second optical path includes the third port but not the first port. The wedge does so by deflecting an optical signal input from the second port, but not an optical signal from the first port. The first birefringent material intersects the first optical path and the second optical path and is disposed between the wedge and the second port along the second optical path.

Abstract: The tunable wavelength division multiplexer is disclosed. The wavelength division multiplexer includes a fiber, a holder, a filter, and an isolator. The fiber carries an optical signal that includes a plurality of channels. The holder has and end and an axis. The holder receives the first fiber in an aperture such that the first fiber is separated from the axis by a distance. The distance is selected to tune the first angle of incidence so that the filter transmits a portion of the optical signal centered around at least one particular wavelength. The optical signal from the fiber impacts the filter at a first angle of incidence. The filter transmits a portion of the optical signal centered around at least one particular wavelength. The isolator is optically coupled with the filter and prevents a first portion of the portion of optical signal transmitted by the filter from returning to the first fiber.

Abstract: A system and method for providing filtering is disclosed. The system and method include providing a first fiber and a second fiber. The first fiber is for carrying a first optical signal. The second fiber is for carrying a second optical signal. The method and system further include providing a holder, a filter, a first wedge, and a third fiber. The holder is for receiving the first optical fiber and the second optical fiber therein. The filter is for filtering the first and second optical signals to provide a first and a second filtered optical signal, respectively. The first wedge is disposed between the holder and the filter. The first wedge is for directing the first optical signal towards the filter in a first path and for directing the second optical signal toward the filter in a second path. The third fiber is for receiving the first filtered optical signal. The fourth optical fiber is for receiving the second filtered optical signal.

Abstract: An improved optical circulator transfers light from a first optical port to a second optical port, and from the second port to a third port. The circulator has reciprocal and non-reciprocal polarization rotators, birefringent beam splitters and combiners, and a birefringent walk-off element as well as a polarization-dependent light bending device comprising two tapered birefringent plates. The light bending device compensates for an angle between a first light beam emanating from the first port and a second light beam propagating to the third port. The existence of this angle allows the first and third fibers to be coupled to the light beams using a single lens.