255 results about "Channel spacing" patented technology

A coolerless photonic integrated circuit (PIC), such as a semiconductor electro-absorption modulator/laser (EML) or a coolerless optical transmitter photonic integrated circuit (TxPIC), may be operated over a wide temperature range at temperatures higher then room temperature without the need for ambient cooling or hermetic packaging. Since there is large scale integration of N optical transmission signal WDM channels on a TxPIC chip, a new DWDM system approach with novel sensing schemes and adaptive algorithms provides intelligent control of the PIC to optimize its performance and to allow optical transmitter and receiver modules in DWDM systems to operate uncooled. Moreover, the wavelength grid of the on-chip channel laser sources may thermally float within a WDM wavelength band where the individual emission wavelengths of the laser sources are not fixed to wavelength peaks along a standardized wavelength grid but rather may move about with changes in ambient temperature. However, control is maintained such that the channel spectral spacing between channels across multiple signal channels, whether such spacing is periodic or aperiodic, between adjacent laser sources in the thermally floating wavelength grid are maintained in a fixed relationship. Means are then provided at an optical receiver to discover and lock onto floating wavelength grid of transmitted WDM signals and thereafter demultiplex the transmitted WDM signals for OE conversion.

Messages are broadcast in a vehicular environment using a network of nodes. Each node includes a transceiver and a processor arranged in a vehicle. A bandwidth of the network is partitioned into a set of channels including a control channel (CCH) and multiple service channel (SCH). Time is partitioned into alternating control channel intervals (CCHI) and service channel intervals (SCHI). A particular node transmits an attention signal indicating intent to access a particular channel to transmit a high priority safety message, wherein the network is designed according to a standard for a vehicular environment. The node then waits a random length backoff time and transmits the high priority safety message related to the vehicular environment after the random length backoff time.

The inventive optical fiber coupler array is capable of providing a low loss, high-coupling coefficient interface with high accuracy and easy alignment between a plurality of optical fibers (or other optical devices) with a first channel-to-channel spacing, and an optical device having a plurality of closely-spaced waveguide interfaces with a second channel-to-channel spacing, where each end of the optical fiber coupler array is configurable to have different channel-to-channel spacing, each matched to a corresponding one of the first and second channel-to-channel spacing. The novel optical coupler array includes a plurality of waveguides (at least one of which may optionally be polarization maintaining), that comprises at least one gradually reduced vanishing core fiber, at least in part embedded within a common housing structure. Alternatively, the novel coupler array may be configured for utilization with at least one of an optical fiber amplifier and an optical fiber laser.

A flexible wavelength switch fabric may be implemented with multiple groups of reconfigurable blocking filters or with multiple multi-in, single out wavelength selective switches. The behaviors of reconfigurable blocking filters are individually settable, such as channel blocking, channel spacing, transmission rate, and default blocking state. Add and drop taps may be added to provide arbitrary add/drop capability. Optical splitters/combiners used may be tunable so that insertion losses may be minimized for the overall network.

A digital phase locked loop (PLL) frequency synthesizer includes a 1-bit numerically controlled oscillator (NCO) to negate the requirement that a VCO frequency be an integer multiple of its reference frequency. Thus, in accordance with the principles of the present invention, a direct digital synthesizer (DDS) or numerically controlled oscillator (NCO) is used to form a frequency divider in a feedback path of a PLL. Thus, a synthesizer with fine frequency control and very fast settling time is disclosed. The conventional integer-ratio relationship between the reference frequency fREF and the synthesized output frequency signal fVCO is overcome by replacement of a conventional VCO divider in a feedback path of a digital PLL with a 1-bit NCO. This allows the reference frequency fREF to be greater than the channel spacing, i.e., the channel spacing can be smaller than the reference frequency fREF. Thus, a much quicker settling time and improved VCO phase noise are provided, either of which results in a significant improvement in the performance of virtually any communications system.

An improved multicarrier modulation system and method, which has the advantages of both isotropic orthogonal transfer algorithm orthogonal frequency division multiplexing (IOTA OFDM) and scalable advanced modulation (SAM), is introduced. The invention is root raised cosine (RRC) OFDM using the most spectrally efficient RRC filter without sacrificing the compact subchannel spacing of OFDM. The invention further provides an adjacent channel interference (ACI) suppression scheme and a modified RRC for better suppressing ACI of RRC OFDM. The ACI suppression scheme can also be applied to SAM with the modified RRC and to IOTA OFDM with a modified IOTA. The invention greatly improves a major problem of conventional OFDM namely ACI due to the use of a wide subchannel filter. Thus, the invention allows OFDM to meet even the strictest ACI requirements, which was not possible by using a conventional raised cosine windowing method.

Switching optical signals containing a plurality of spectral channels characterized by a predetermined channel spacing is described. A selected beam deflector array may be selected from among a plurality of available beam deflector arrays configured to accommodate spectral channels of different channel spacings. The selected beam deflector array is configured to accommodate spectral channels of the predetermined channel spacing. The spectral channels are selectively optically coupled to the selected beam deflector array, which selectively optically couples the spectral channels between one or more input ports and one or more output ports.

A method and apparatus is provided for tracking a thermally floating wavelength signal channel grid generated at an optical transmitter (Tx) in an optical transmission system or optical network where the wavelengths of the individual Tx signal channels may move in wavelength due to, for example, changes in ambient temperature at the optical transmitter but the channel spacing between Tx signal channels along the thermally floating Tx wavelength grid remains constant. An optical receiver (Rx) is provided that has a demultiplexed signal channel grid that may have a different channel spacing from that of the floating Tx wavelength grid, that is either larger, the same as, or smaller Rx grid spacing compared to the Tx grid spacing, and includes a number of demultiplexed channel signal outputs along an Rx channel grid in excess of the number of Tx signal channels on the Tx channel grid so that the optical receiver is capable of detecting the floating Tx channel grid and providing electrical output signals representative of the Tx channel signals transported over the optical network.

A method and system for transmitting information in a wavelength division multiplex (WDM) or other suitable multichannel optical communication system includes receiving a multichannel signal having a symbol rate and comprising a plurality of non-intensity modulated optical information signals. The non-intensity modulated optical information signals have a minimum channel spacing comprising a multiple of the symbol rate within 0.4 to 0.6 of an integer. The non-intensity modulated optical information signals are separated from the multichannel signal and each converted into an intensity modulated optical information signal using an asymmetric interferometer. A data signal is recovered from the intensity modulated optical information signal.

Provided are a method of tuning a coding rate and applying an unequal error protection for an adaptive video transmission, and a video transmission/reception apparatus using the method. The video transmission apparatus may include: a coding rate tuner to predict, as a channel capacity of a subsequent channel interval, an estimated channel capacity value fed back from the video reception apparatus, and to tune video and channel coding rates within the predicted channel capacity; a video encoder to perform video encoding of video frames at the tuned video coding rate, and to generate a video packet; and a forward error correction (FEC) encoder to apply the unequal error protection based on a length of the video packet and a type of the video frames included in the video packet, and to perform channel encoding of the video packet at the tuned channel coding rate to generate a bitstream.

Disclosed by way of exemplary embodiments, a 40/50/10 Gb/s Optical Transceivers/transponders which use opto-electronic components at data rates collectively that are lower than or equal to half the data rate , using two optical duobinary carriers. More specifically, the exemplary embodiments of the disclosed optical transceivers/transponders relate to a 43 Gb/s 300 pin MSA and a 43˜56 Gb/s CFP MSA module, both include a two-carrier optical transceiver and the appropriate hardware architecture and MSA standard interfaces. The two-carrier optical transceiver is composed of a pair of 10 Gb/s optical transmitters, each using band-limited duobinary modulation at 20˜28 Gb/s. The wavelength channel spacing can be as little as 19˜25 GHz. The same principle is applied to a 100 Gb/s CFP module, which is composed of four tunable 10 Gb/s optical transmitters, with the channel spacing between optical carriers up to a few nanometers.

A monolithically integrated wavelength switchable laser comprises three coupled Fabry-Perot cavities. The length and consequently the free spectral range of the first cavity are designed such that the resonant peaks correspond substantially to a set of discrete operating wavelengths separated by a constant channel spacing. The second cavity has a slightly different length so that only one resonant peak coincides with one of the resonant peaks of the first cavity over the spectral window of the material gain. The lasing action occurs at the common resonant wavelength. The two cavities are coupled through a third short cavity that produces a certain coupling loss and phase relationship between the first and the second cavities in order to achieve an optimal mode selectivity of the combined cavity laser. In operation, both the first and the second cavities are forward biased to provide optical gains for the laser action. The second cavity is tuned by varying the refractive index of at least a portion of the waveguide within the cavity through an electrical means, resulting in wavelength switching of the laser among the set of discrete operating wavelengths as determined by the first cavity.

A method for sensing channel availability in a wireless network includes receiving a measurement request message which includes a channel interval list. A first channel interval in the list includes information associated with a first starting channel number, a first number of channels, and first linkage information of the channel interval list. The method includes processing information associated with the message, generating a first list of contiguous channels, and performing at least first channel measurement to determine a first channel availability for each of the first list of contiguous channels. The method also includes determining whether the channel interval list further includes a second channel interval that needs to be processed based on at least first linkage information, and if needed, generating a second list of contiguous channels and performing at least second channel measurement to determine a second channel availability for each of the second list of contiguous channels.

The present invention is directed toward a laser wavelength locking scheme suitable for incorporation into WDM systems having channel spacings of 25 GHz or less. In a preferred embodiment, light output from the laser is supplied to a filtering element, such as an in-fiber Bragg grating or an etalon, and photodetectors are used to sense light transmitted through and either reflected by the filtering element or input to the filtering element. A measured ratio corresponding to a quotient of the photocurrents generated by the photodetectors is calculated and compared to a desired ratio corresponding to a measured temperature of the filtering element when the filtering element transmits the desired wavelength to be locked. Based on the comparison of the desired and measured ratios, a temperature error value is calculated which is used to adjust the laser temperature, as well as the laser wavelength. Accordingly, the temperature of the filtering element, for example, influences the laser temperature, so that wavelength variations stemming from temperature induced changes in the filtering element and other components in the laser package can be compensated, and the output wavelength can remain substantially fixed.

The disclosure relates to a tunable 50 GHz and 100 GHz channel spacing DWDM transceiver, and methods of making and using the same. The transceiver comprises an electro-absorption modulation laser (EML), a system board configured to compare a preset wavelength with an actual emission wavelength of the EML, a microcontroller and one or more associated registers configured to communicate with the system board, a temperature controlling circuit configured to stabilize the actual emission wavelength of the EML; and a wavelength meter connected to the output of the EML and having an output connected to the system board. The system board may be configured to provide a feedback loop from the EML to the microcontroller. The transceiver, suitable for 50 GHz channel spacing standards, can be made from existing standard transceivers and can switch between 50 GHz and 100 GHz channel spacing modes.

Method and system for band blocking in an optical telecommunication network. According to an embodiment, the present invention provides a system for optical network. The system includes an input that is configured to receive an input signal through a first optical input. The system also includes a band splitting module that is coupled to the input. The band splitting module is configured to separate the input signal into a plurality of bands. The plurality of bands includes a first band and a second band. The first band includes a first plurality of wave channels. The first plurality of wave channels is characterized by a first channel spacing. The second band includes a second plurality of wave channels, which is characterized by a second channel spacing.

A modulator, and demodulator, apparatus and method for use in a multiple sub-channel communication system is taught. A commutator is employed for fractionally sampling, or distributing, signals from, or to, a multiple channel polyphase filter. The filter is coupled with a discrete Fourier transform, or its inverse, such that the relationship between the base-band sampling rate of a plurality of sub-channel signals, the frequency spacing of the sub-channel signals, and the sampling rate of a composite signal can be related by any rational number, thereby freeing designers to optimize system design respecting channel spacing, bandwidth, and signaling rates. The advantages of the present invention are realized by adjusting the interpolation and decimation rates of the filter, and by adjusting the resolution and decimation rates of the transform.