40 results about "Optical cdma" patented technology

A polarization independent (PI) interferometer design that can be built from standard optical components is described. Based upon a Michelson interferometer, the PI interferometer uses a 50/50 splitter and Faraday Rotator Mirrors (FM's). The interferometer achieves good optical characteristics, such as high extinction ratio (ER) and low insertion loss (IL). Lack of polarization sensitivity reduces interferometer construction tolerances and cost, enhances performance and utility, and expands the scope of interferometric based devices. Such characteristics can be used to construct flexible, high performance, polarization insensitive, multi-rate, self-calibrating, optical DPSK receivers, power combiners, optical filters and interleavers, all-optical switches, and cascaded interferometers. Since polarization is not maintained in standard fiber optic networks, a PI-DPSK receiver allows for use of more sensitive DPSK communications over fiber, without need for costly polarization control hardware. Other applications of PI interferometers include optical CDMA, secure communications, optical coherence tomography (OCT), and temporal gratings with ultra-precise timing.

An optical fiber communications system using spread spectrum code division multiple access techniques to achieve better bandwidth utilization. A transmitting user in the system encodes the optical signal using a first coding mask, and a receiving user decodes the received signal using two decoding masks, all of the masks having lengths N. The first mask is divided into two sections of lengths N/2 each, one of the sections defining a first sub-code of length N/2, while the other section blocks light. Each of the second and third masks is also divided into two sections, which correspond to the two sections of the first mask. The section of the second mask corresponding to the coded section of the first mask has a second code that is identical to the first code, and the section of the second mask corresponding to the blocked section of the first mask is also blocked. The section of the third mask corresponding to coded section of the first mask has a third code that is complementary to the first code, and the section of the third mask corresponding to the blocked section of the first mask is also blocked. Some users on the system have masks in which the first of the two sections are blocked and the second of the two sections are coded, while other users have masks in which the second of the two sections are blocked and the first of the two sections are coded. The first codes used to code the encoding masks are selected from a set of unipolar codes that are derived from a set of balanced bipolar orthogonal codes.

Apparatus and system for transmitting and receiving optical code division multiple access data over an optical network. The apparatus comprises a spectral phase decoder for decoding the encoded optical signal to produce a decoded signal, a time gate for temporally extracting a user signal from the decoded signal, and a demodulator that is operable to extract user data from the user signal. The system preferably comprises a source for generating a sequence of optical pulses, each optical pulse comprising a plurality of spectral lines uniformly spaced in frequency so as to define a frequency bin, a data modulator associated with a subscriber and operable to modulate the sequence of pulses using subscriber data to produce a modulated data signals and a Hadamard encoder associated with the data modulator and operable to spectrally encode the modulated data signal to produce an encoded data signal.

A two-dimensional wavelength/time optical CDMA system employing balanced-modified pseudo random noise (PN) matrix codes is provided. Through an inverse-exclusive OR operation of a pair of modified PN code, the balanced codes are generated as optical CDMA codes in the form of a new matrix. When the codes are applied to an optical CDMA system to perform encoding and decoding, if the same number of channels as the number (M−1) of subgroups of the codes are connected, the system becomes an MAI-free system, and even if the number of channels connected is twice the number of the subgroups, an error-free system can be established. Accordingly, the number of channels that can be used simultaneously is doubled compared to the prior art method such that the economical efficiency of the optical CDMA system improves.

An optical CDMA encoder-decoder is constructed by combining arrayed-waveguide gratings, matrix optical switches, and delay lines, otherwise by combining arrayed-waveguide gratings and variable delay lines, thus providing an encoding process that a wavelength change with respect to time in optical pulses.

A method and device are provided for automatically generating a key and a conjugate key to be used in an optical code division multiple access system. The method comprises applying a down conversion process to pump input light to thereby produce down converted broadband signal and idler fields that are complex conjugates of each other. The signal and idler fields thus serve as the key and its conjugate. Also provided according to the invention is a method for use in coding/decoding a signal in an optical code division multiple access system.

The present invention relates generally to an optical CDMA transmission system and method employing differential optical encoding and bipolar decoding. Differential encoding and bipolar decoding may be performed at the bit level, wherein differential phase encoding and decoding occurs on an entire composite signal. Differential encoding and bipolar decoding may also be performed at the chip level, wherein differential phase encoding and decoding occurs on individual spectral components of a given signal.

A system and method for performing phase-encoded optical Code Division Multiple Access (CDMA). A transmitter encodes digital data onto a wavelength of an optical signal using a codeword, splits the optical signal into a plurality of beams having separated frequency components, selectively phase-shifts the beams in accordance with the codeword, recombines the beams into the optical signal, and transmits the optical signal. The receiver receives the optical signal, splits the optical signal into a plurality of beams having separated frequency components, selectively phase-shifts the beams in accordance with the codeword, recombining the beams into the optical signal, and decodes the digital data from a wavelength of the optical signal using the codeword.

The invention discloses a DS-OCDMA system coding and decoding sampling optical fiber grating and its producing method, it belongs to coding and decoding technology field of optical CDMA communication, the character is: modulating average optical fiber grating using new sampling structure, making its -1 grade reflection peak of reflected spectrum have the needed coding and decoding function. It only needs to average phasic moulding board, compared to current method, it decreases producing needed precision, and increases producing flexibility, so the producing cost is reduced, and it is suitable to be produced in great force.

The optical CDMA access network with common light source includes optical line terminal (OLT). Characters of OLT are that OLT uses common light source. The invention solves technique of common light source in broadband and technique of OLT in high performance so as to meet requirements on explosive social information quantity, and multiple services of operation. Beneficial effects of the invention are: using WDM technique to realize multimedia service for whole operation; optical network terminal (ONU) for each user does not contains laser light source since common light source is adopted so as to realize low cost; OLT realizes functions of resources configuration and network management of access network effectively.

The invention discloses a novel large user capacity optical code division multiple access codec. After a light signal composed of a number of wavelengths is input from the input port of a waveguide, wavelengths which meet the resonance condition of each micro-ring at the same time pass micro-rings which are connected in series and are output from the downloaded end of another waveguide, and other wavelengths which do not meet the condition are passed away from the transfer port of the waveguide. A thermal resistance device on each micro-ring is adjusted to control the wavelength change of an annular resonator, so as to realize wavelength selection. A phase shifter on a bus is controlled to adjust the phase corresponding to the reflection wave of each group of micro-ring, so as to complete the specific phase change of different wavelengths. Wavelength-phase two-dimensional coding is realized. In a similar fashion, each wavelength light signal is successively reflected in the same manner. The phase is respectively modulated. Coding through light signals is realized. A decoder is in the reverse arrangement structure of a coder. According to the invention, the user capacity of an optical code division multiple access system is expanded; the performance of the codec is improved; and as the number of the columns of the micro-rings which are connected in series increases, the user capacity is in e exponential growth.

A data transmission method utilizing optical CDMA technique includes utilizing electric domain CDMA to carry out electric domain spread spectrum coding by sending end and changing it to be optical signal by optical modulator, entering optical signal into another optical modulator to carry out optical domain spread spectrum coding and entering it into optical coder for coding, using optical decoder to carry out decoding and using photoelectric detector to restore it to be electric signal at receiving end then utilizing electric domain integrator and decision gate circuit to restore original data.

An optical code division multiple access communication system using a processor processes at least one collimated input beam which has been modulated with a data signal to produce multiple time-delayed output beams. The multiple time-delayed output beams are spatially distributed and independently phase shifted. An integration lens receives the phase modulated output beams and reintegrates the phase modulated output beams into a single encoded beam with a time series chip sequence. The integrated encoded beam is transmitted. A receiving system includes a processor to process the encoded collimated light beams received from a transmitter to produce multiple time-delayed output beams. The multiple time-delayed output beams are spatially distributed and independently phase shifted. An integration lens receives the phase-shifted output beams and reintegrates the phase-shifted output beams into a single decoded beam.

An encoder according to the present invention is an encoder for encoding an optical wavelength-multiplexed signal compliant with optical CDMA into a code having a code pattern, including: L optical fibers 36 and 42 (where L is an integer equal to or greater than two) each having a plurality of gratings 37 to 47; and a circulator 52 for coupling the plurality of optical fibers 36 and 42. The code pattern contains time bins t1 to t3. A plurality of wavelengths λ1, λ4 and λ5 are assigned to the time bin t1. If a sum of an optical path difference in each optical fiber from the grating which reflects the optical signal of the wavelength λ1 to the grating which reflects the optical signal of the wavelength λ4 is calculated for all of the optical fibers 36 and 42, the sum equals zero.

This invention provides an OCDMA system including an optical line terminal OLT and multiple ONU, and said OLT includes multiple connected optical transceivers and coder/decoders and a first optical coupler, said multiple coder-decoders are connected with the first optical coupler, said system also includes an optical distribution network RN containing a third coupler and multiple coders/decoders connected with it separately, and each ONU includes an optical transceiver, each coder/decoder of said OLT is connected with the third coupler of the RN and its corresponding decoder via the first coupler and each of the ONU is connected with a corresponding decoder of the RN.

Disclosed herein are a CDMA optical system and encoder and decoder included therein. Time domain encoding means creates a time domain code having a sequence according to inputted data bits or a complementary code which is complementary to the time domain code. An optical modulation means selectively outputs lights, in which the lights are incident upon the optical modulation means from the outside, to two output leads, respectively, according to chip bits of the time domain code or the complementary code. A wavelength domain encoding means encodes the light outputted from a first output lead of the optical modulation means to a wavelength domain sequence (two dimensional code), transmits the wavelength code to the base station, encodes the light outputted from a second output lead to a complementary sequence of the wavelength domain sequence, and transmits the complementary code of the two dimensional code to the base station.

A new method and system for Optical Code Division Multiple Access (OCDMA) transmission, in which channel selection and rejection are based on dynamic self-heterodyne filtering using differential time delays applied to the data-modulated signals to code and decode the transmissions in each channel. Mach-Zender Interferometers having characteristic delays between their arms are a simple way of performing this coding and decoding. The technique enables the use of narrow linewidth sources and low spectrum spreading. Consequently this technique can be used in next-generation all-optical dynamic networks allowing bandwidth sharing on the one hand, while at the same time eliminating the need for network management and optical switching. Preliminary theoretical calculations predict the system support of up to 15 channels at a data rate of 1 GHz.

The invention provides a dynamic code reconstruction control system based on a security protection strategy. The system comprises a security strategy module, an optical code resource configuration module and a control module. The system has the following advantages: the dynamic code reconstruction control system based on the security protection strategy is the core of a dynamic code reconstruction optical CDMA secure transmissions system with an anti-interception function, is applied to an anti-interception optical fiber communication secure transmission system, and is widely applied to military communication systems in the national defense military field and fiber communication systems with high security requirements such as government organs, enterprise groups, communication between islands and the like in social and economic fields.

The present invention is one incoherent chirp-encoding optical CDMA access system. The optical encoder consists of linear chirp fiber grating, optical circulator, fiber delay line network and optical synthesizer. The data bit modulating ultrashort pulse laser outputs wideband ultrashort optical pulses, which are shunted in a shunt and passed through separate fiber delay line to form two ultrashort pulse sequences. After passing through two optical circulators and chirp fiber grating, two expanded pulse sequences are synthesized into one bipolar chirp-encoded frequency expanding signal. Via a similar process in the optical decoder, one decoded strong output pulse is formed. The present invention has complete fiber structure of coder, and is easy to be integrated, great in system capacity and low in code error rate.