Optical waveguides – Polarization without modulation
Reexamination Certificate
2001-11-13
2004-05-25
Glick, Edward J. (Department: 2882)
Optical waveguides
Polarization without modulation
C385S033000, C385S036000, C359S490020, C359S490020, C359S490020
Reexamination Certificate
active
06741764
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed generally to a fiber optic device, and more particularly to devices that can split or combine light signals according to the polarization of the light signals.
BACKGROUND
Optical fibers find many uses for directing beams of light between two points. Optical fibers have been developed to have low loss, low dispersion, polarization maintaining properties and can also act as amplifiers. As a result, optical fiber systems find widespread use, for example in optical communication applications and remote sensing.
Wavelength, optical power and polarization are important properties of the light signals propagating in a fiber optic system. Components within the system may modify the propagation of the signals by changing one or more of these properties. For example, multiple signals may be transmitted through a single fiber optic by combining the outputs from a plurality of laser transmitters, each transmitter having an output wavelength that is restricted to a unique spectral band. Amplitude and/or frequency modulation may be used to encode information on the transmitter outputs. The polarization property may be used for network operations that include the tuning, multiplexing, demultiplexing and switching of light signals, for example.
Systems that utilize the polarization property of light often require light signals to be separated or combined according to their polarization state. A single fiber optic device may be designed to carry out both processes, separating signals from a combined input that propagates through the device in a first direction and combining polarized signals that propagate through the device in the opposite direction.
Polarization beam separator/combiners for use in fiber optic systems may use non-guiding optical components to separate/combine the optical signals as they propagate through the device along free-space optical paths. Collimating lenses are typically used to couple the light propagating along the free-space optical paths to the input/output waveguides with a one-to-one correspondence between lenses and waveguides. Thus a polarization separator/combiner with three input/output waveguides typically incorporates three lenses that must be accurately aligned with respect to the waveguides and the free-space optical paths.
Conventional polarization separator/combiners share several common disadvantages that derive from the one-to-one correspondence between fibers and focusing optical systems. For example, the low-loss propagation of light is facilitated by the accurate alignment of the optical focusing assemblies to the optical fibers. Alignment tolerances may be of the order of one micron and must be maintained against both temperature variations and vibration during the operational lifetime of the device. Typically, the optical components are housed in a mechanical alignment and support assembly that increases in complexity, size and cost with the number optical coupling components. It is, therefore, disadvantageous to use a dedicated optical focusing assembly to couple each of the optical fibers
SUMMARY OF THE INVENTION
Generally, the present invention relates to a device for use in a fiber optic system that may be a communication system, a sensing system or other system using guided-wave optical components.
Reducing the number of lenses required to couple the waveguides and the free-space paths offers the dual advantages of a reduced component count and simplified alignment. It is, therefore, advantageous to provide a polarization splitter/combiner incorporating non-guiding optical components that interact with light propagating along free space paths, the free space paths coupled to a number, N, of input/output waveguides by a number, M, of focusing elements where M<N.
One embodiment of the invention is directed to an optical device that includes a first waveguide, a second waveguide, and a birefringent optical system with bi-directional, polarization-dependent free-space paths. One of the bidirectional, polarization-dependent, free-space paths couples at least the first waveguide to the second waveguide, the birefringent optical system including at least one prism for bending one of the polarization-dependent paths in a clockwise direction and one of the polarization-dependent paths in a counterclockwise direction.
Another embodiment of the invention is directed to an optical device that includes a first waveguide, at least a second waveguide, and a folded optical system with bi-directional, polarization-dependent free-space paths that couple the first waveguide and the at least a second waveguide. The optical system includes a birefringent path separator that is traversed by light propagating along the free-space paths in a first direction and in a second direction approximately opposite to the first direction.
Another embodiment of the invention is directed to an optical device that includes a first waveguide, a second waveguide coupled to the first waveguide via a first bi-directional, polarization dependent path, and a third waveguide coupled to the first waveguide via a second bi-directional, polarization dependent path. A Wollaston prism is disposed on the first and second bi-directional, polarization dependent paths. The first and second bi-directional, polarization dependent paths overlap between the first waveguide and the Wollaston prism. A first converging optical subsystem is disposed to couple light between the second waveguide and the Wollaston prism and between the third waveguide and the Wollaston prism. The first converging optical subsystem includes at least one focusing element common to the first and the second bi-directional, polarization dependent paths.
Another embodiment of the invention is directed to an optical device that includes a first waveguide, a second waveguide, a third waveguide, and a converging optical system. A birefringent optical system defines a first polarized optical path between the first waveguide and the second waveguide and defines a second polarized optical path between the first waveguide and the third waveguide. The polarization of light propagating along the first polarized optical path is orthogonally polarized to the polarization of light propagating along the second polarized optical path. The converging optical system includes at least one focusing element disposed on both the first and second polarized optical paths where the first polarized optical path is spatially separated from the second polarized optical path.
Another embodiment of the invention is directed to an optical communications system that includes a transmitting unit, a receiving unit and an optical transport system coupled to carry optical information signals between the transmitting unit and the receiving unit. At least one of the transmitting unit, the receiving unit, and the optical transport system include an optical device for coupling a first light beam to a second polarized light beam and a first beam to an orthogonally polarized light beam. The optical device includes a first waveguide and a second waveguide, and a birefringent optical system with bi-directional, polarization-dependent free-space paths. One of the paths couples at least the first waveguide to the second waveguide. The birefringent optical system includes at least one prism for bending one of the polarization-dependent paths in a clockwise direction and bending one of the polarization-dependent paths in a counterclockwise direction.
Another embodiment of the invention is directed to an optical communications system that includes a transmitting unit, a receiving unit and an optical transport system coupled to carry optical information signals between the transmitting unit and the receiving unit. At least one of the transmitting unit, the receiving unit, and the optical transport includes an optical device for coupling a first light beam to a second polarized light beam. The optical device includes a first waveguide, a second waveguide and a folded optical system with bi-directional, polarizatio
Lu Liang-Ju
Wu Pingfan P.
Yang Zhicheng
Zhang Boying Barry
ADC Telecommunications Inc.
Barber Therese
Carlson, Caspers Vandenburgh & Lindquist
Glick Edward J.
LandOfFree
Polarization beam separator and combiner does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Polarization beam separator and combiner, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polarization beam separator and combiner will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3269594