96 results about "Optical time division multiplexing" patented technology

The invention discloses a distributed optical fiber sensing system for measuring temperature, strain and vibration simultaneously. Based on an Optical Time Domain Reflectometry (ODTR) multiplexing technology, optical time-division multiplexing unequal-width dipulse serves as detection light, coherent detection technologies of Brillouin scattering signals and Rayleigh scattering signals are merged,and a set of distributed optical fiber sensing system which can conduct single-ended measuring on the temperature, strain and vibration is achieved; meanwhile, the measuring range of the vibration frequency can reach the MHz level, and the problems are solved that a traditional ODTR system can only measure the temperature strain or the static strain while cannot timely respond to the dynamic change, or it is hard to measure the temperature strain and the static strain simultaneously, or the measurable range of the vibration frequency is limited by the length of sensing optical fiber. The distributed optical fiber sensing system can conduct single-ended measuring, and is simple in structure, easy to implement, and good in application prospect.

A dispersion compensation controlling apparatus used in a very high-speed optical communication system adopting optical time division multiplexing system comprises a first specific frequency component detecting unit (2a) detecting a first specific frequency component in a baseband spectrum in a transmission optical signal inputted to a receiving side over a transmission fiber as a transmission line (6a), a first intensity detecting unit (3a) detecting information on an intensity of the first specific frequency component detected by the first specific frequency component detecting unit (2a), and a polarization-mode dispersion controlling unit (220a) controlling a polarization-mode dispersion quantity of the transmission line (6a) such that the intensity of the first specific frequency component detected by the first intensity detecting unit (3a) becomes the maximum, thereby easily detecting and compensating polarization-mode dispersion generated in a high-speed optical signal.

The invention discloses a single-fiber bidirectional transmission system based on mode division multiplexing. The single-fiber bidirectional transmission system based on the division multiplexing mainly comprises two optical signal input units, two optical signal output units and a mode division multiplexing and demultiplexing unit, wherein the mode division multiplexing and demultiplexing unit comprises two mode-type multiplexers which are connected through few-mode fiber. Polarization multiplexing optical signals are generated by the signal input units, the polarization multiplexing optical signals are enabled to be coupled into a mode field of the few-mode fiber by the mode-type multiplexer to finish the mode division multiplexing, the polarization multiplexing optical signals carried by the mode field are sent to the other mode-type multiplexer through the few-mode fiber, the received polarization multiplexing optical signals are enabled to be coupled into single-mode fiber by the other mode-type multiplexer and sent to the optical signal output units through the single-mode fiber, polarization diversity, mixing and balance detection are carried out on the received optical signals by the signal output units, then the received optical signals are changed into electric signals and then changed into digital signals. According to the single-fiber bidirectional transmission system based on the mode division multiplexing, the few-mode fiber is used for overcoming Rayleigh backward scattering effect, single-fiber bidirectional transmission is achieved, and use efficiency of optical fiber and wavelength resources is improved.

The invention discloses a method and a system for time division multiplexing of transmitting channels to overcome the defect of lack of using transmitting channel redundancy in a multi-antenna system to reduce transmitting channels. The method includes: using a first group of transmitting channels on a first frequency band to transmit signals to a first geographic region through a first group of antenna units according to a first channel bandwidth in a first time interval; and using the first group of transmitting channels on a second frequency band to transmit signals in a second time interval after the first time interval, or using the first group of transmitting channels on a third group of antenna units to transmit signals, wherein the pass band width of the first channel is smaller than or equal to the width of the first frequency band, and the second frequency band is not identical to the first frequency band. By means of time division multiplexing of transmitting channels among different frequency bands and / or different antenna units, the defect of lack of using transmitting channel redundancy in the multi-antenna system to reduce the transmitting channels in the prior art is overcome.

A multiplexing / demultiplexing system has a multiplexor that includes a first plurality of optical switches having a plurality of outputs and a first plurality of optical delay elements coupled to the optical switches. A source of optical light is coupled to the delay elements, and an optical combiner is coupled to the plurality of outputs and a source of framing pulses. A demultiplexor includes a first and second splitter, and a threshold detector coupled to the first splitter. The demultiplexor further includes a second plurality of optical delay elements coupled to the threshold detector, and a second plurality of optical switches coupled to the second splitter and the second plurality of delay elements.

An optical communication network using a communication system which is combined optical time-division multiplexing and optical wavelength-division multiplexing. The electric / optical converter converts an electric signal strings, which are input from the outside, into optical burst signals by selectively using a plurality of types of optical wavelengths. The network controller controls the optical wavelength selected by the electric / optical converter and the output timing of the optical burst signals for each one of the optical burst signals so that the optical burst signals received by the OLT are time-division multiplexed and wavelength-division multiplexed. By combining optical time-division multiplexing and optical wavelength-division multiplexing, an optical communication network of which the transmission band is wider than a TDMA system can be provided with a lower cost and lower facility scale than a WDM system.

The invention discloses an optical fiber wireless RoF passive optical network realizing method based on an optical code division multiplexing (OCDM). In an optical line terminal (OLT) RoF center station, a signal realizes double-sideband modulation, three paths of generated carrier components are respectively modulated with wired and wireless user data and are not subjected to modulation. The signal is coupled to an optical fiber channel after coded by the OCDM, transmitted to an optical distribution network (ODN) and allocated to each optical network unit (ONU). The ONU carries out OCDM decoding on the received signal, then three paths of components are separated, one path of components is directly sent to a wired user terminal after subjected to photoelectric detection, the other two paths of components enter an RoF base station for carrying out beat frequency to obtain a radio frequency signal, the radio frequency signal is subjected to ECDMA (Electric Code Division Multiple Access) coding and transmitted through an antenna after subjected to electric amplification, and a wireless user terminal obtains a required signal through ECDMA decoding. The invention provides an effective path for realizing wired / wireless secrecy access in a PON (Passive Optical Network) system.

Disclosed is a passive optical network system using a time division multiplexing scheme. According to one exemplary embodiment, the passive optical network system includes a plurality of optical network units (ONUs); an optical line terminal (OLT) to be connected to the plurality of ONUs for communication and to transmit and receive an optical signal to and from the plurality of ONUs using a time division multiplexing (TDM) scheme, wherein each of the plurality of ONUs includes a light source that generates an optical signal with a predetermined intensity even in burst-off state; and an optical filter disposed on a receiving path of an optical receiver of the OLT to filter out an optical noise signal received from an ONU in burst-off state among the plurality of ONUs.

A time division multiplex transmission system transmits information on multiple channels by using a transmission path with variable time division multiplexing. The variable time division multiplex transmission system of this invention is equipped with multiple channel devices 30 and a single transmission path 5 connected to these multiple channel devices. The multiple channel devices 30 transmit or receive data over the transmission path. Additionally, the system is equipped with a circuit that determines consecutive time slots for using the transmission path, and each of the channel devices transmits or receives data using consecutive time slots. Data can be transmitted in two or more different transmission bands, and the different transmission bands are realized by making the number of time slots used for a communication frame different.

The invention discloses a time division multiplexing (TDM)-based low-reflectivity triangle spectrum-shaped fiber grating sensing system. The system mainly comprises a distribution feedback laser, an electro-optical modulator, a circulator, an optical amplifier, a triangle spectrum-shaped fiber grating sensor, a high-speed optical detector, a pulse signal generator and a signal acquisition device, wherein the distribution feedback laser is used for emitting narrow line-width laser; pulse signal light is formed by the narrow line-width laser through the electro-optical modulator or is generated by internal modulation through the distribution feedback laser; the pulse light passes through the circulator and then is reflected by a triangle spectrum-shaped fiber grating; the reflected light passes through the circulator to enter the optical amplifier and is amplified into the high-speed optical detector; and a light signal is converted into an electrical signal through the high-speed optical detector, and the electrical signal is converted into a digital signal and is processed through the signal acquisition device. In the system, the distribution feedback laser and the low-reflectivity triangle spectrum-shaped fiber grating sensor are combined, a large-scale fiber grating sensing network is constructed through TDM, and thousands of sensors are multiplexed on a single fiber, so that the costs of a light source and a wavelength detection device are reduced.

Methods and apparatus for interrogating sets of optical elements having characteristic wavelengths spanning a sweep range while avoiding overlapping reflections from the different sets when performing a wavelength sweep are provided. One example method generally includes introducing a pulse of light, by an optical source, into an optical waveguide to interrogate at least first and second sets of optical elements, wherein the optical elements within each set have different characteristic wavelengths and wherein the first and second sets are separated in time such that a first time window over which light is reflected from the optical elements in the first set and reaches a receiver does not overlap with a second time window over which light is reflected from the optical elements in the second set and reaches the receiver; and processing the reflected light to determine one or more parameters corresponding to the optical elements.

A novel integrated multiple-rate optical time division multiplexing (OTDM) module is disclosed. An integrated set of modulators generates optical RZ signal streams which are then time-delayed by a set of integrated optical delay switching and combining arrays and interleaved to produce an OTDM signal. The integrated optical delay switching and combining arrays are adapted to be controllably set to various delays to facilitate interleaving of many possible bit-rates. Such an approach alleviates stability problems offered by conventional fiber-based OTDM technology, increases flexibility, aids in reducing the size, complexity, and cost. Furthermore, the OTDM chip of the present invention offers fine tuning capabilities thereby allowing for slight adjustments in the interleaving of optical signal streams if needed. The present invention also provides for the integration of an optical pulse source chip and a multiple-rate OTDM chip onto a single substrate or platform using hybrid packaging technology.

Provided are an Optical Network Unit (ONU) for low latency packet transmission in a Time Division Multiplexing-Passive Optical Network (TDM-PON), a method of operating the ONU, and an apparatus for controlling the ONU. The method includes: receiving, from a base station, first bandwidth allocation information regarding a bandwidth allocated by the base station to a terminal for uplink packet transmission; and transmitting a bandwidth allocation request, which is based on the received first bandwidth allocation information, to an Optical Line Terminal (OLT) before completing packet reception from the base station.

The invention discloses an ultra-wideband radio over fiber positioning system, and belongs to the technical field of ultra-wideband radio communication. In the positioning system, ultra-wideband sensor nodes are sequentially connected by fibers to form an annular ultra-wideband sensor network distributed in a detection area. Optical time division multiplexing is realized by accurately controlling the lengths of the fibers among the sensor nodes, and ultra-wideband signals detected by different sensors are separated to different time slots of a signal period of an ultra-wideband signal source, so that signals of respective sensor nodes are distinguished and recognized. Ultra-wideband signals carrying position information of an object to be detected are received by the ultra-wideband sensor nodes and then transmitted back to a central processing unit through the fibers to process the positioning signals. Complexity of software and hardware of the sensor nodes can be effectively reduced while ensuring high ultra-wideband positioning accuracy, and the positioning system has low transmission loss and high system stability.

The invention relates to a navigation enhancement signal modulation method and system, and the method comprises the following steps of (1) channel coding: respectively carrying out channel coding on a low-speed message and a high-speed message; (2) PRN code mapping: mapping the low-speed message after channel coding into a path of PRN code sequence, and mapping the high-speed message after channel coding into a path of PRN code sequence to obtain two paths of PRN code sequences; (3) code period time division: according to a code period time division pattern, time division multiplexing the two PRN code sequences into one signal according to a code period; and (4) baseband waveform modulation: performing baseband waveform modulation on one path of signal obtained after code period time division multiplexing to obtain a baseband signal. Compared to the mixed structure of BPSK and R-CSK using QPSK modulation, the navigation enhancement signal modulation method and system adopts a code period time division technology, and the spread spectrum code period of the modulated low-speed message and the spread spectrum code period of the modulated high-speed message are broadcasted after time division according to the time division pattern of a fixed structure. All power can be used for signal tracking and demodulation.

The invention provides a clock recovery method for a high-speed optical time-division multiplexing system. In the method, a base frequency clock is put into a high-speed optical time-division multiplexing data tape in an additional phase modulation manner, so that co-transmission of high-speed optical time-division multiplexing data and the base frequency clock is realized; and base frequency clock recovery of the optical time-division multiplexing system can be realized by only separating the base frequency clock out at a receiving end. According to the method, the defect of the need of the optical phase-locked loop structure for the recovery of a clock from optical time-division multiplexing data streams in the prior art is overcome, and a foundation is laid for the research of a high-speed optical signal processing unit orienting to a next generation all-optical communication network. The method has the characteristics of novel scheme, simple structure and high compatibility, and has extensive application prospects in the aspects of optical fiber communication system, all-optical switch networking, and the like.

The invention provides a tunable multi-wavelength erbium-doped fiber laser and a method of the tunable multi-wavelength erbium-doped fiber laser. The tunable multi-wavelength erbium-doped fiber laser comprises a tunable pump light source, erbium-doped fibers, polarization controllers, an opto-isolator, a tunable comb filter, a nonlinear fiber loop mirror and an output coupler. Switching of different wavelength intervals and tuning of wave peak positions in each wavelength interval are achieved by adjusting the incident laser polarization state of the M-Z interference filter; adjustment on the wavelength number and the spectral range is achieved by adjusting the working state of the nonlinear fiber loop mirror; the wavelength number is accurately controlled by adjusting the pumping power. The tunable multi-wavelength erbium-doped fiber laser is formed by all optical devices, and is good in compatibility, convenient to tune, low in cost, capable of achieving stable multi-wavelength output at the indoor temperature and capable of meeting the demands of a wavelength division multiplexing system or the optical time division multiplexing communication technology for a multi-wavelength laser source.

Methods and apparatus for fast sweeping a spectral bandwidth in order to distinguish among signals received from effectively wavelength division multiplexed (WDMed) and time division multiplexed (TDMed) optical components on a single fiber. For some embodiments, a method for interrogating optical elements having characteristic wavelengths spanning a sweep range is provided. The method generally includes introducing a pulse of light, by an optical source, into an optical waveguide to interrogate at least a first set of optical elements having different characteristic wavelengths by performing a sweep of wavelengths over a period of the pulse, wherein the period is less than a round-trip time for light reflected from an optical element closest to the optical source to reach a receiver and processing the reflected light to determine a parameter based on the times at which signals are received.

The invention discloses a demodulation system and method of a fiber grating sensor based on edge filtering and time division multiplexing. A plurality of fiber F-P lasers with different center wavelengths transmit laser signals of respective central wavelengths. The laser signals through a fiber into a circulator. The circulator injects a combined laser into a sensing unit. The sensing unit comprises a plurality of sets of sensing arrays connected in series. Each set of sensing arrays comprises a plurality of fiber gratings connected in series corresponding to different center wavelengths. Each of the sensing arrays is connected by a time division delay fiber. The circulator simultaneously receives the optical signal fed back by the sensing unit, and separates the different wavelengths ofthe incident light and transmits the same to a processing unit. The processing unit amplifies the optical signals of different wavelengths and performs edge filtering. The processing unit demodulatesthe fiber grating sensing arrays with the same wavelength type according to the signal return time. High frequency demodulation of a large-capacity fiber grating sensing array on a single fiber can beachieved by combining edge filtering and time division multiplexing.

An approach is provided for managing off-network virtual connections. A first management channel is mapped to a second management channel for transport of management information over an optical time-division-multiplexing (TDM) network that includes an off-network portion. The off-network portion corresponds to a third party provider. The first management channel corresponds to an electrical connection and the second management channel corresponds to an optical connection.

A polarization-maintaining time-interleaved optical analog-to-digital converter sequentially comprises a mode-locked laser, an optical time division multiplexing frequency multiplication module, a spectrum slicing frequency multiplication module, an optical amplification module, an electro-optic intensity modulation module, a polarization-maintaining connection module, an optical demultiplexing module, a photoelectric converting and processing module and a synchronization module which are connected through polarization-maintaining optical fibers. According to the polarization-maintaining time-interleaved optical analog-to-digital converter, it is guaranteed that the polarization state of an optical sampling pulse sequence in the process of optical time division multiplexing frequency multiplication, spectrum slicing frequency multiplication, optical amplification and transmission does not change on the basis of the polarization-maintaining structure, polarized light emitted by the mode-locked laser always coincides with the polarization axis direction of an electrooptical modulator, and therefore optical pulse amplitude fluctuation caused by polarization dependence is eliminated. A high-stable frequency source of the synchronization module provides same frequency references for the mode-locked laser and an electric analog-to-digital converter, therefore, it is guaranteed that the electric analog-to-digital converter has few shakes on the time interval that a photoelectric detector outputs sampling points of an electronic pulse sequence, and the precision is improved.

An optical system for modulating and switching logical information-bits in optical communication networks and optical computers. The system includes at least one input, at least one interference device, and at least one output. The interference device receives radiation from the input along multiple orientations at different timings. The interference device produces one interference pattern from a group of different interference patterns so that it can produce a pattern according to the timings, and directs this pattern toward the one output. The output receives the interference pattern produced by the one interference device and selectively emits radiation from the system according to the interference pattern produced according to the timings. The system has two basic versions. In the first version the system operates as an all-optical modulator for generating very short pulses. The second version of the system operates as an all-optical switch. In both versions the system has two operational modes. In the first a control beam activates the system. In the second the system is self-activated. The narrow pulses that the system produces allow the use of Dense Time Division Multiplexing (DTDM) and the self-activating mode of the system allows using Code Division deMultiplexing (CDM) for switching and packet routing.

At present, low-cost optical network units in TWDM-PON (time division multiplexing-passive optical network) and user amount expansion are key research issues in optical access networks. an embodiment of the invention provides a TWDM-PON optical access network structure for annular subnet extension and provides specific structures of certain devices in the network and a control method of the whole network and particularly provides a novel optical network unit structure supportive to subnet extension, an optical network unit side subnet structure and a structure of a subnet optical network unit. By adoption of the network structure and the equipment, users in subnets can share a tunable laser with the optical network units while receiving of downlink signals is unaffected; gains of uplink and downlink optical amplifiers can be tuned according to intensity of uplink and downlink optical signals, and accordingly quality of signals in the optical network units and optical network unit side subnets can be optimized; in addition, TWDM-PON user amount expansion can be carried out effectively while low terminal cost is kept.

The invention relates to a self-adaptive transmission method based on bit division multiplexing. The method comprises the steps that (a), a transmission mode is selected according to a predicted value of the current channel state; (b), channel encoding and bit interleaving are independently conducted on input information bit in each bit pipeline, and an encoded bit is obtained; (c) constellation labeling is conducted on encoded bits output by the bit pipelines at the same time, and a sending symbol is obtained and output; (d) the sending symbol is received; (e) the current channel state information and a transmission mode are combined to conduct demodulation decoding on the received sending symbol, and demodulation decoding results of all the bit pipelines are obtained, wherein the steps (a), (b) and (c) are executed by a sending end, and the steps (d) and (e) are executed by a receiving end. The invention further relates to a self-adaptive transmission system based on bit division multiplexing. Compared with a traditional self-adaptive encoding modulation method, the average transmission rate of users is effectively improved, and the problems that channel resource allocation flexibility is low and a constellation diagram changes are solved.

The invention provides a quantum key channel transmission method and system based on optical time division multiplexing. The method comprises steps of S1, based on the wavelength division multiplexing mechanism, allocating a wavelength resource for the data service to obtain the data channel, and allocating a wavelength resource for the quantum key to obtain the quantum key channel and the measuring base channel; S2, based on the data channel, allocating a data channel resource for one data service and transmitting the data service; S3, based on the quantum key channel, transmitting the quantum key related to the data service by the optical time division multiplexing mode; and S4, based on the measuring base channel, transmitting measurement base information related to the quantum key by the optical time division multiplexing mode. The invention utilizes the optical time division multiplexing technology to segment the optical network wavelength resources to realize the dynamic construction of the quantum key channel and ensure that the optical network can realize the efficient quantum key distribution and that the real-time and efficient use of the whole network resources is achieved under the premise that the resources are limited and the security of the data service is guaranteed.

The embodiments of the present invention disclose an External Cavity Laser (ECL), relate to the field of Wave Division Multiplexing-Passive Optical Network (WDM-PON) technology, and effectively solve a problem of unstable output optical power of the ECL caused by polarization dependence. The ECL includes a gain medium, a filter, and a Faraday Rotator Mirror (FRM). The gain medium, the filter and the FRM constitute an oscillation cavity, and light emitted by the gain medium oscillates back and forth in the oscillation cavity.

The optical time division multiplexer generates a time-division-multiplexed optical signal by time-division-multiplexing optical signals of a plurality of channels, the carrier-wave phases of which are shifted with respect to one another. The circulator guides the multiplexed optical signals split by the optical splitter to the optical interference device and the superimposed light outputted from the optical interference device is guided to the optical intensity detector. The optical interference device extends the pulse width of the multiplexed optical signal to a width equal to or more than the bit interval and superimposes the extended light of an adjacent bit onto the extended light. The optical intensity detector detects the intensity of the superimposed light outputted by the optical interference device. The temperature regulator controls the temperature of the modulator so that the phase difference of the carrier waves constituting the optical signal trains is to be a half wavelength.

A TDM comprising: (a) at least two wavelength-tunable devices for outputting a signal, each wavelength-tunable device being adapted to change signal wavelength in response to a change signal; (b) a plurality of on-off gates, one on-off gate being coupled to the output of each wavelength-tunable device such that, when a gate is on, the signal of its respective wavelength-tunable device passes through, and, when it is off, the signal of its respective wavelength-tunable device does not pass through, the gates being configured such that a gate is switched off when its respective wavelength-tunable device receives a change signal, and, when one gate is turned off, another gate is turned on; and (c) a combiner coupled to the outputs of all the gates for combining the outputs on a single transmission line.