Chorum Technologies Inc.

Ec-optics Technology Inc.

Macro-vision Communications, Inc.

Charles Wong

Jian-Yu Liu

Kuang-Yi Wu

Yen-Chen Chen

Ye Li

Ming Xu

Tizhi Huang

Chongchang Mao

Chi-Hao Cheng

Leo Yu-Yu Lin

A wavelength division multiplexing/demultiplexing device is presented utilizing a polarization-based filter to separate odd and even wavelengths, or upper and lower channels of an input optical signal. The wavelength filter first converts the input signal to a predetermined polarization. A series of birefringent waveplates provide a polarization-dependent optical transmission function such that the polarized beam is decomposed into a first beam component carrying the first spectral band at a first polarization and a second beam component carrying the second spectral band at a second, orthogonal polarization. A beam displacer spatially separates the beam components into a pair of orthogonally-polarized beams. A quarter-wave plate converts these orthogonally-polarized beams into a pair of circularly-polarized beams, which are reflected by a mirror back along parallel optical paths through the quarter-wave plate, beam displacer, and waveplates. In the return pass, the quarter-wave plate converts the reflected circularly-polarized beams into two orthogonally-polarized beams having polarizations that are rotated by 90 degrees from those in the forward pass. The waveplates further purify the spectral characteristics of the reflected beams and maintain the polarization of one of the reflected beams, while rotating the polarization of the other reflected beam by 90 degrees so that both reflected beams have substantially the same polarization. A routing element directs one of the reflected beams exiting the waveplates to a first output port and the other reflected beam to a second output port.

Compact wavelength filter using optical birefringence and reflective elements

An optical wavelength division multiplex (WDM) demultiplexer can be provided in substantially passive form. In one embodiment a wavelength filter separates alternate channels to provide a first output containing even-numbered channels and a second output containing odd-numbered channels, each output having channels separated by a bandwidth twice the channel separation bandwidth of the original WDM signal.

Programmable optical add/drop multiplexer

An optical equalizer for use primarily with an erbium-doped fiber amplifier has an initial polarizer that convert the input beam to a predetermined polarization, followed by a series of dynamically-adjustable sinusoidal filters that provide attenuation as a sinusoidal function of beam wavelength. Each of the sinusoidal filters has a first liquid crystal cell adjustably rotating the polarization of the beam from the preceding polarizer. This is followed by a second optical element that retards the beam as a sinusoidal function of beam wavelength. For example, the second optical element can be a birefringent crystal that provided a fixed degree of retardance to the beam and a second liquid crystal cell that provides a variable degree of retardance, thereby allowing adjustment of the center frequency of the sinusoidal function. Finally, a third liquid crystal cell adjustably rotates the polarization of the beam. A final polarizer provides amplitude control of the beam based on the polarization rotations introduced by the first and third liquid crystal cells. A controller provides control signals to the liquid crystal cells of each sinusoidal filter so that their combined sinusoidal attenuation functions produce a desired equalization curve.

Dynamic gain equalizer for optical amplifiers

The inventive filter forms a four filtering stage device from two filtering stages and a reflective stage. This greatly reduces the noise level in a WDM signal, wherein the signal is one of the odd channels and the even channels, while the noise is present on the other of the odd channels and the even channels. The first stage separates the WDM signal and noise into their polarization components, rotates the components of one of the signal and the noise, and recombines the components of the signal, while blocking a portion of the noise. This output is passed to the second stage which repeats the operation of the first stage. The output of the second stage is then reflected by the reflecting stage back to the second stage, and subsequently the first stage, for processing in reverse order. The inventive filter, via the mirror in the reflecting stage, reduce dispersion of the light during processing.

Wide transmission optical comb filter with wide pass band and wide stop band

A stacked waveplate device that performs an optical wavelength filtering function is described which provides dispersion with a first magnitude and a first sign for a first optical path having a first output polarization and which provides a second dispersion with a substantially equal but oppositely-signed dispersion for a second optical path defining an output having an orthogonal polarization to the polarization of said first output path. Optical paths are configured to pass through first and second stacked waveplate devices sequentially with the optical dispersion of said second device having an approximately equal magnitude but opposite sign compared to the optical dispersion of the first optical stacked waveplate devices so as to provide canceling or compensation of optical dispersion. A device is configured to use cancellation or compensation of dispersion in sequential stacked waveplate devices to provide outputs with characteristics similar to outputs of previous stacked waveplate devices but with substantially reduced dispersion characteristics.

Dispersion compensation for optical systems

A twisted nematic liquid crystal-based electro-optic modulator with a twist angle between 0&deg; and 90&deg;, and preferably between 50&deg; and 80&deg; is provided. The modulator provides a relatively rapid switching time such as less than about 50 milliseconds, and provides relatively large extinction ratios, such as greater than &minus;25 dB. Preferably the liquid crystal entrance director differs from the polarization direction by a beta angle of about 15&deg;.

Acute twist nematic (ATN) liquid crystal device for optical communication applications

Programmable optical add/drop device

Programmable optical multiplexer

Optical communication system having a liquid crystal routing switch

A twisted nematic liquid crystal-based electro-optic modulator with a twist angle between 0.degree. and 90.degree., and preferably between 50.degree. and 80.degree. is provided. The modulator provides a relatively rapid switching time such as less than about 50 milliseconds, and provides relatively large extinction ratios, such as greater than -25 dB. Preferably the liquid crystal entrance director differs from the polarization direction by a beta angle of about 15.degree..

Growing community of inventors

Richardson, TX, United States of America

Charles Wong