1594 results about "Dispersion compensation" patented technology

Polarization mode dispersion in an optical signal transmitted through a waveguide of a communications system is compensated by separating the dispersed signal into components corresponding to principal polarization states. The components are delayed by respective delays differing by a delay increment which is controlled to correspond to the dispersion delay and the delayed components are recombined to provide a dispersion compensated optical output signal. Each of the delays is provided by an chirped Bragg reflector forming part of a delay line, the Bragg reflectors comprising optical fibres with chirped intracore index gratings. Transducers or temperature controllers acting on one of the fibres allows dimensional control of the grating periodicity such that the position of Bragg reflection is variable. Wavelength division multiplexed optical signals are compensated using sampled gratings which allow a common Bragg reflection position for each wavelength.

Methods, systems and computer program products for generating parameters for software dispersion compensation in optical coherence tomography (OCT) systems are provided. Raw spectral interferogram data is acquired for a given lateral position on a sample and a given reference reflection. A trial spectral phase corresponding to each wavenumber sample of the acquired spectral interferogram data is postulated. The acquired raw spectral data and the postulated trial spectral phase data are assembled into trial complex spectrum data. Trial A-scan data is computed by performing an inverse Fourier transform on the trial complex spectrum data and determining the magnitude of a result.

A system, process and software arrangement are provided to compensate for a dispersion in at least one portion of an image. In particular, information associated with the portion of the image is obtained. The portion of the image can be associated with an interference signal that includes a first electromagnetic radiation received from a sample and a second electromagnetic radiation received from a reference. The dispersion in the at least one portion of the image can be compensated by controlling a phase of at least one spectral component of the interference signal.

A method and apparatus of compensating for compact digital domain chromatic dispersion. The distortion of an optical signal due to chromatic dispersion is compensated by a digital signal processing in the electrical domain, either prior to the optical transmitter or following the receiver. The circular coefficient approximation and sub-band processing reduce the amount of computations to execute a given level of chromatic dispersion compensation compared to a direct finite impulse response filter implementation.

In accordance with the invention, an optical communication system is provided with one or more automatic dispersion compensation modules. Each module has an adjustable dispersion element, a data integrity monitor and a feedback network whereby the monitor adjusts the dispersion element to optimize system performance. In a preferred embodiment the dispersion compensating modules comprise chirped fiber Bragg gratings in which the chirp is induced in the grating by passing a current along distributed thin film heaters deposited along the length of the fiber. The magnitude of the applied current determines the dispersion of the grating. A data integrity monitor is configured to sense the integrity of transmitted data and to provide electrical feedback for controlling the current applied to the grating.

A method of recovering a clock signal from an optical signal received through an optical communications system. A digital sample stream is processed to generate a dispersion compensated signal. The dispersion compensated signal is then tapped to obtain upper side band and lower side, band signals of each received polarization of the optical signal. The upper side band sand lower side band signals are then processed to compensate polarization dependent impairments and the clock recovered from the resulting optimized.

A method of suppressing effects of aliasing in a system for digitally processing a high speed signal having a symbol rate of 1/T. The high speed signal is sampled at a fractional multiple (N) of the symbol rate, wherein 1<N<2, to generate a corresponding sample stream, and filtered using a low-pass filter characteristic having a cut-off frequency corresponding to 1/2T. Phase distortions due to the filtering are compensated by digitally processing the sample stream.

A diffraction grating of non-uniform strength is introduced into an optical waveguide by modulating its width. The waveguide may be fabricated using one of several planar processing techniques. Varying the size, position, and/or thickness of the grating teeth provides the desired variation of grating strength. Certain functional variations of grating strength suppress side-lobe levels in the grating reflection and transmission spectra. This process, termed apodization, is necessary for precise wavelength filtering and dispersion compensation. If desired, different periodicity gratings can be introduced in each side of the waveguide, multiple periodicities can be superimposed, the grating can be angled with respect to the waveguide, and the grating period and phase can be varied.

An example apparatus comprises an optical transmitter which includes a first processor and at least two optical modulators. The first processor is configured to generate a first electronic representation for each of at least two optical signals for carrying payload data modulated according to a one-dimensional (1-D) modulation format, and to induce on respective ones of the first electronic representations an amount of dispersion that depends on a power-weighted accumulated dispersion (AD_PW) of a transmission link through which the at least two optical signals are to be transmitted thereby generating complex-valued electronic representations of pre-dispersion-compensated optical signals. Each of the at least two optical modulators modulate a respective analog version corresponding to a respective one of the complex-valued electronic representations onto a polarization of an optical carrier.

A ring-laser system that includes a plurality of ring-laser gain elements and a spectral-beam-combining output stage configured to combine a plurality of beams coming from the gain elements into an output beam and that includes chromatic-dispersion compensation. In some embodiments, the output stage includes a plurality of highly reflective dielectric-coated focussing elements. In some embodiments, the output stage includes a plurality of high-efficiency dielectric-coated grating elements. In some embodiments, the output stage includes a mostly reflective but partially transmissive output mirror and a highly reflective beam-reversing mirror configured to reflect a majority of a backward-traveling signal beam such that it becomes forward traveling. In some embodiments, each gain element further includes a photonic-crystal-rod power amplifier. Some embodiments have an amplitude modulator configured to pulse the plurality of beams, and a timing controller configured to synchronize the pulses of the plurality of beams. Some embodiments further include a non-linear wavelength-conversion device.

An optical transmission network includes an optical transmitter photonic integrated circuit (TxPIC) chip, utilized in an optical transmitter and has a plurality of monolithic modulated sources integrated for multiple signal channels on the same semiconductor chip is provided with channel equalization at the optical receiver side of the network that permits one or more such integrated modulated sources in the TxPIC chip to be out of specification thereby increasing the chip yield and reducing manufacturing costs in the deployment of such TxPIC chips. FEC error counts at the FEC decoder on the optical receiver side of the network includes counters that accumulate a plurality of bit pattern-dependent error counts based on different N-bit patterns in the received data bit stream. The accumulated counts of different N-bit patterns are utilized to provide for corrections to threshold and phase relative to the bit eye pattern as well as provided for weight coefficients for the optical receiver equalization system. The deployment of this type of equalization in a digital OEO REGEN network substantially reduces, if not eliminates, the need for dispersion compensating fiber (DCF) or EDFAs in an optical link of the network and enhances the optical receiver tolerance to chromatic dispersion (CD) so that an increase in chip yield is realized for TxPIC chips not operating with acceptable operational parameters, particularly with a desired frequency chirp parameter relative to at least one of the TxPIC modulated sources.

According to various embodiments and aspects of the present invention, there is provided a dynamically tunable thin film interference coating including one or more layers with thermo-optically tunable refractive index. Tunable layers within thin film interference coatings enable a new family of thin film active devices for the filtering, control, modulation of light. Active thin film structures can be used directly or integrated into a variety of photonic subsystems to make tunable lasers, tunable add-drop filters for fiber optic telecommunications, tunable polarizers, tunable dispersion compensation filters, and many other devices.

In a chromatic dispersion compensator, an optical signal directing unit such as an optical circulator or a directional coupler having a first, second, third and fourth ports. The optical signal directing unit directs an optical signal inputted from one of the ports to another port of the ports. A reflection-type compensator including a dispersion compensating fiber, a reflecting portion and changing unit for changing a polarization direction of a reciprocating signal light, in which the dispersion compensating fiber is connected to the reflecting portion via the changing unit. An input transmission path which is connected to the first port; and an output transmission path which is connected to the fourth port so that the signal light is outputted from the fourth port. The reflection-type compensating unit is connected to one of the second and third ports, and the chirped grating is connected to the other port.

There is provided an optical amplifier for reducing the optical output power difference and/or obtaining high output power across a wide wavelength band. The optical amplifier comprises a plurality of optical amplifier units connected in two or more stages. At least one of the optical amplifier units comprises a first optical component of a single input and N outputs that has an optical-demultiplexing function, and P units of optical amplification means for the individual amplification of light that is output from P (where 1<=P<=N) output terminals selected from the N (integer) output terminals of the first optical component. Second optical components are provided to the input side of the first optical component or between the output side of the first optical component and the input side of the optical amplification means. The second optical components are optical components having chromatic dispersion compensation functions, optical components having functions designed to compensate for wavelength dependency output power difference, or optical components demonstrating other required effects. The optical components are DCFs, FBGs, SMFs, optical filters, attenuators, or the like. The second optical components are provided nonselectively or selectively.

The present invention aims at realizing a dispersion compensating method capable of readily conducting automatic compensation of waveform degradation caused by dispersion characteristics of an optical transmission path, and at providing a dispersion compensating apparatus and an optical transmission system, of a smaller size at a reduced cost. To this end, the dispersion compensating apparatus of the present invention comprises: a variable dispersion compensator for compensating for the dispersion of optical signal input via an optical transmission path; a bit error information monitoring circuit for generating bit error information of a received signal output from the variable dispersion compensator via an optical receiving circuit; and a controlling circuit for optimally controlling a wavelength dispersion value of the variable dispersion compensator based on the bit error information from the bit error information monitoring circuit.