Abstract: An optical spectrum analyzer (10), receiving a multi-channel optical signal (12). The optical signal (12) is passed through an optical isolator (14) and a fiber coupler (16) to a tunable optical filter. The tunable optical filter comprises one or more fiber Bragg gratings (18) inscribed in a length of optical fiber. The optical fiber is mounted on a means operable to apply a variable strain to the fiber, to they tune the peak wavelength of the Bragg grating (18) over a desired wavelength range, the tunable optical filter thereby reflecting each channel of the input signal (12) in turn. The detector (20) therefore detects a signal only if the input signal (12) contains wavelengths corresponding to the reflection wavelength of a grating (18).

Abstract: The present invention provides a single fibre bidirectional optical transmission system capable of realizing the extension of a single fibre bidirectional long distance at a moderate price.

Abstract: A multi-channel optical device includes a first plurality of optical structures formed simultaneously using vapor deposition on different regions of a common substrate. Each optical structure in the plurality is comprised of a plurality of thin-film layers. The thickness of each layer in a given optical structure corresponds to a wavelength associated with one of the channels. A reflector has a surface parallel to the common substrate, and a transport region is disposed between the first plurality of optical structures and the reflector. An aperture is disposed at one end of the transport region, and the first plurality of optical structures are disposed along a length of the transport region. When an input optical signal is provided to the aperture, the device functions as an optical demultiplexer and output optical signals associated with different ones of the channels are generated at separate positions along a length of the transport region.

Abstract: An optical wavelength router separates an input signal into two complementary output signals. A beamsplitter of the wavelength router separates the input signal into a first beam and a second beam. A first resonator reflects the first beam producing a group delay that is dependent on wavelength. Similarly, a second resonator reflects the second beam. The center wavelength of the second resonator is offset relative to that of the first resonator by one half of the free spectral range of the first resonator, so that the resonance frequencies of the second resonator are matched to the anti-resonance frequencies of the first resonator. The beams reflected by the resonators interfere within the beamsplitter to produce two output signals containing complementary subsets of the spectrum of the input signal (e.g., even optical channels are routed to a first output port and the odd optical channels are routed to a second output port).

Abstract: An add/drop node is disclosed. The add/drop node includes a first filter configured to receive a light beam having a plurality of channels. The first filter is also configured to direct channels having wavelengths falling within a plurality of first wavelength bands to a transition waveguide. The add/drop node also includes a second filter configured to receive the channels directed to the transition waveguide. The second filter is configured to direct channels having wavelengths falling within a plurality of second wavelength bands to a drop waveguide. The first filter and/or the second filter can be tunable.

Abstract: A single-sideband dense wavelength division multiplexing optical communication system and method are disclosed that achieve an increased throughput by moving the carrier wavelengths from the center of the corresponding channel band and suppressing one of the sidebands associated with each channel band. Most of the power is placed in the selected sideband and additional bandwidth is available to increase the throughput within the selected sideband. An electrical signal is modulated to provide a passband signal without low frequency components. The disclosed modulation scheme shifts the carrier wavelengths within the wavelength grid to provide additional bandwidth for the selected sideband in each channel band. Generally, the bandwidth (and thus, throughput) that is available to the selected sideband increases by a factor of two.

Abstract: An optical add-drop multiplexer comprises an optical switch (10) for selection of a desired wavelength channel to be extracted, a pre-processing channel assembly (20), an optical reflector (50), an optical extractor (60), a post-processing channel assembly (30), and an optical coupler (40) aligned with the post-processing channel assembly. The pre-processing channel assembly transmits a multiplexed signal stream containing a plurality of channels. The optical reflector directs light rays emitted from the pre-processing channel assembly into the optical extractor. The optical extractor comprises a narrow bandpass filter (62) that allows a desired channel to pass therethrough and reflects other unextracted channels. The desired channel can be dropped by switching to a corresponding output port of the optical switch. The optical reflector directs light rays reflected from the optical extractor to the post-processing channel assembly. The optical coupler combines the unextracted channels and an insertion channel.

Abstract: The WDM receiver includes a wavelength demultiplexer, a detector array and a signal extractor. The wavelength demultiplexer receives an n-channel optical input signal and transmits the n-channel optical input signal to m optical outputs. Each of the optical outputs receives a wavelength band centered at a different wavelength. The wavelength bands have a center-to-center wavelength spacing of &Dgr;&lgr;′. The detector array is composed of m detector elements coupled to the wavelength demultiplexer. Each of the detector elements generates a detection signal in response to light received from one of the optical outputs of the wavelength demultiplexer. The signal extractor receives the detection signals from the detector array and converts the detection signals to an n-channel receiver output signal, each channel of which corresponds to a different one of the n channels of the optical input signal.

Abstract: Objects of the present invention are to reduce the number of optical filters, and to improve crosstalk characteristics of periodic optical filters. WDM signals are converted into vestigial-side-band signals collectively using a periodic optical filter. As an example, light signals having odd number wavelengths (wavelengths &lgr;1, &lgr;3, &lgr;5) and light signals having even number wavelengths (wavelengths &lgr;2, &lgr;4, &lgr;6) are wavelength-multiplexed in the first optical wavelength multiplexer, and are then filtered by a periodic narrow band-pass optical filter to convert the light signals into vestigial-side-band (VSB) signals. Then, the vestigial-side-band signals are combined by the second optical wavelength multiplexer. Such an interleave configuration enables suppression of crosstalk caused by adjacent channels.

Abstract: A gain equalizer which equalizes gain versus wavelength characteristics of an optical amplifier. The gain versus wavelength characteristics of the optical amplifier include first, second and third gain peaks in a wavelength band with the second gain peak being between the first and third gain peaks. The optical amplifier amplifies an input signal in accordance with the gain versus wavelength characteristics to produce an output signal. The gain equalizer includes first, second and third optical filters having first, second and third transparency characteristics, respectively. The first, second and third transparency characteristics are periodic waveforms having different periods related to the wavelength difference between the first and third gain peaks. The second transparency characteristic is a periodic waveform having a period equal to 1/(2n) of the period of the waveform of the first transparency characteristic.

Abstract: The present invention provides a WDM transmission system that can multiplex/demultiplex and transmit wavelength division multiplexing signals, where signal lights have a different signal bandwidth, in a status without much deterioration of transmission quality. For the WDM signals P0, 10 Gbit/s signals with a 25 GHz bandwidth are arrayed in odd channels on a grid with a 50 GHz interval, and 40 Gbit/s signals with a 75 GHz bandwidth are arrayed in even channels. The WDM signals P0 are demultiplexed by the interleaver 1, then are demultiplexed by the interleavers 2 and 3. The central frequency of the transmission bands-of the ports A1 and B1 are shifted from the central frequency of the 10 Gbit/s signals so that the overlapping portion of the transmission band of the ports A1 and B1 substantially match the signal band of the channel ch [4i-2] (i is an integer of 1 or higher). By this, only 40 Gbit/s signals in the channel ch [4i-2] are output from the port B1.

Abstract: A wavelength stabilizing filter has a wavelength transmission characteristic curve that has its peak in a wavelength located between a first continuous set band and a second continuous set band longer in wavelength than the first set band, and that linearly drops from the peak toward the shorter wavelength side than the first set band and also toward the longer wavelength side longer than the second set band. A control unit generates a control signal needed to enable an optical tunable filter to extract signal light with a predetermined wavelength from an inputted WDM signal, based on light transmitted through the wavelength stabilizing filter.

Abstract: The objective is an optical transmission unit capable of coupling and branching signal lights of individual wavelengths at a data rate of 10 Gbits/s. In order to achieve the objective, DCFs are provided and proper values of dispersion compensation are given, so that different characteristics depending on the respective wavelengths to be coupled, split and pass through without being split are obtained. The signal lights are amplified by a plurality of low-excitation optical amplifiers to regain their light levels which are weakened due to using an optical coupler, branching filter and DCF together, thereby enabling a long-distance transmission.

Abstract: This invention discloses an optical device that includes a wavelength-selective optical transmission system. The wavelength-selective optical transmission system further includes a first waveguide for transmitting a multiplexed optical signal therethrough. The wavelength-selective optical transmission system further includes a second waveguide coupled to the first waveguide wherein a least one of the first and second waveguides having a set of wavelength-selective Bragg gratings disposed near a coupling section between the first and second waveguides. One of the first and second waveguides has an aspect ratio, i.e., a ratio of a thickness divided by a width, is no greater than 0.75.

Abstract: Optical infinite impulse response (IIR) filters are efficient polarization mode dispersion (PMD) compensators, requiring fewer stages than finite impulse response (FIR) filters. IIR filter architectures incorporating allpass filters allow the phase and magnitude compensation to be addressed separately. An IIR filter PMD compensator comprising a polarization beam splitter, allpass filters, polarization rotation devices, a 2×2 filter, and a polarization beam combiner optically coupled is described.

Abstract: A selected wavelength variable optical filter for selecting and outputting the signal lights of the desired wavelengths from the light multiplexing light lights of a plurality of wavelengths. When the multiplexing factor of the WDM signal light increases, the number of selected wavelength variable optical filters used in the AOTF device or the like also increases, resulting in increase of manufacturing cost.

Abstract: A wavelength converter configured to filter out solely lightwaves required to be wavelength converted from the input broadband of wavelength division multiplexed (WDM) lightwaves, which are wavelength converted by use of four-wave mixing (FWM). Frequency interval of the input WDM lightwaves is broadened or reduced in comparison of the frequency interval of the WDM lightwaves inputted to the wavelength converted. The frequency interval variation techniques using the wavelength converter, it can be realized to transfer from transmission lines less influenced by inter-channel crosstalk due to FWM to the different transmission lines strongly influenced by inter-channel crosstalk due to FWM, and vice versa. In one embodiment, the invention employs difference frequency generation (DFG) instead of FWM.

Abstract: A double-ring optical wavelength multiplex network is disclosed, which includes multiple optical transmission apparatuses that can reduce the unit cost of initially installing a small optical network while providing the flexibility to expand. For multiplexed optical signals arriving at a node, the optical transmission apparatus “drops” selected wavelengths for local delivery and “passes” others for continued transmission on the network. For optical signals originating (“added”) at the node, the optical transmission apparatus wavelength multiplexes the “added” signals with the “passing” signals for transmission on the network. For “added” signals, the optical transmission apparatus blocks “passing” signals of the same wavelength.

Abstract: A wavelength selector for transmitting radiation of multiple wavelengths. The wavelength selector includes a four-fiber collimator and provides a first input, first output, second input, and second output channel. The first input channel carries radiation of multiple wavelengths. The second input channel carries the radiation of a first wavelength to be added to the first input channel. The second output channel receives the radiation of a predetermined wavelength that is to be dropped. A switch member with a plurality of filters is movable among a plurality of positions. When the switch member is in a first position, the radiation carried by the first input channel reaches the first filter, and the radiation of the first wavelength carried by the second input channel reaches the second filter. The second output channel receives the radiation of a predetermined wavelength carried by the first input channel.

Abstract: A precise, tunable, low loss add/drop filter for use in fiber optic communication systems utilizes a cascaded system of Mach Zender-like stages, along with reflective elements to return passed channels to the output pass+add signal while transmitted signal(s) appear at the drop port. The optional add signal follows the reverse path of the drop signal and is added to the pass signal.

Abstract: A communications network has a plurality of nodes interconnected by an optical transmission medium. The transmission medium is capable of a carrying a plurality of wavelengths organized into bands. A filter at each node for drops a band associated therewith and passively forwards other bands through the transmission medium. A device is provided at each node for adding a band to the transmission medium. Communication can be established directly between a pair of nodes in the network sharing a common band without the active intervention of any intervening node. This allows the network to be protocol independent. Also, the low losses incurred by the passive filters permit relatively long path lengths without optical amplification.

Abstract: An optical component array that has essentially equal path loss for each channel routed through a switching node in a re-insertion configuration and the bypass channels. An array input carrying a plurality of optical channels is coupled to a first node input. Consistent, low transmission loss through a switching node is achieved by a single fiber-beam-fiber transition. The low transmission loss is summed with other array losses to be within 3 dB of the insertion loss of a bypass path. In a particular configuration, a routing array with three switching nodes is loss-balanced to the bypass path. In another embodiment, a multi-channel filter stub in the bypass path improves residual signal suppression when a node is switched to an add/drop configuration.

Abstract: Method and system for selectively adding and dropping selected wavelength components &lgr;=&lgr;k1 and &lgr;=&lgr;k2 (1≦k1≦k2≦K) in a light signal having a sequence of wavelengths &lgr;k (k=1, 2, . . . , K), using a dual fiber collimator at each end of an OADM device that contains an optical filter that transmits a selected wavelength &lgr;k1 and reflects the other wavelengths &lgr;k. Connecting two optical communication terminals in a network allows addition and dropping of a selected wavelength. Estimated total optical insertion losses, between the common port and the express port, for 2×2 and 3×3 add/drop combinations are 0.4 dB and 0.8 dB, respectively.

Abstract: Disclosed is an apparatus for controlling wavelength-division-multiplexed light wherein overall power of wavelength-division-multiplexed light is rendered constant through control for uniformalizing the level of only one wave of maximum power, and wherein the levels of respective channels are made substantially uniform. Optical level control means controls the optical level of propagating wavelength-division-multiplexed light, and a portion of the wavelength-division-multiplexed light output from the output level control means is branched to a tunable optical filter, which selectively outputs the light of each wavelength contained in the wavelength-division-multiplexed light. The light of each wavelength output from the optical filter is photoelectrically converted to an electric signal by photoelectric conversion means.

Abstract: An optical modulation apparatus includes an optical signal input section, an optical signal propagation path, an optical modulator that modulates the phase of optical signals in at least two of a plurality of optical paths, and a wavelength selective filter that selectively reflects and transmits. Optical signals input via the input section are divided into a plurality of optical paths at a branching point and phase modulated by the phase modulator, that divides the optical path into a plurality of optical paths. Light transmitted by the filter is output via the output section, while light reflected by the filter travels back along the optical path and is again phase modulated by the phase modulator combined at the branching point and output from the input section as an intensity modulated optical signal.

Abstract: A tuneable optical filter includes a moveable filter plate and an associated optical region for filtering an input radiation beam to provide corresponding filtered output radiation. The optical region has spatially varying filtration properties. Piezoelectric actuating elements are provided for moving the filter plate and its associated optical region relative to the beam for selecting a portion of the optical region for use in filtering the beam and thereby tuning the filter. The actuating elements are operable when driven by electrical signals to repetitively engage or be in repetitively slidable contact and thereby impart a lateral force to a surface of the filter plate for moving the optical region relative to the beam in at least one dimension. The filter is especially suitable for use in optical communication systems where there arises a need for occasional system reconfiguration involving retuning optical filters of the system.

Abstract: Methods and apparatuses are contemplated for sharing optical sources in an optical network, which typically reduces the number of optical sources needed to operate the optical network.

Abstract: An optical demultiplexing system demultiplexes a multiplex which has at least three levels of granularity and includes m interleaved bands of wavelengths each of which includes p wavelengths. The system includes a 1-to-m deinterleaving demultiplexer for demultiplexing the multiplex into m bands of wavelengths and a 1-to-p deinterleaving demultiplexer for demultiplexing each of the m bands into p wavelengths. The numbers m and p are mutually prime.

Abstract: A communications network has a plurality of nodes interconnected by an optical transmission medium. The transmission medium is capable of a carrying a plurality of wavelengths organized into bands. A filter at each node for drops a band associated therewith and passively forwards other bands through the transmission medium. A device is provided at each node for adding a band to the transmission medium. Communication can be established directly between a pair of nodes in the network sharing a common band without the active intervention of any intervening node. This allows the network to be protocol independent. Also, the low losses incurred by the passive filters permit relatively long path lengths without optical amplification.

Abstract: A reconfigurable non-blocking Optical Add/Drop Module (OADM). The OADM is tunable to drop one or more target channels from an optical signal without interfering with any channels between a starting channel and the dropped channels. During tuning, all of the channels in the optical signal are expressed. In one embodiment of the OADM, two tunable optical filters are optically coupled in a cascade series such that one or more channels may be dropped by tuning both to the dropped channels. The optical filters are electronically coupled to a common controller that controls the operation of each of the tunable filters. The filters are tuned separately to reach the target dropped channels without interfering with any intermediate channels.

Abstract: A WDM optical source, in adopting a spectrum-sliced method, advantageously needs neither an optical source with specific generation wavelength nor a wavelength-stabilizing circuit for stabilizing wavelength. Affording high power and a very narrow line width, the WDM optical source can provide a broadcasting service without signal distortion by a chromatic dispersion effect and also avoids the expense of an amplifier and/or external modulator, thereby relieving subscribers of the economical burden. The practical use of WDM-PON and of WDM-PON using an inventive WDM optical source can therefore be brought to fruition and broadcasting service can be provided economically.

Abstract: The present invention relates to an optical transmission system and a channel assigning method with structure to reduce dispersion of power levels among signals dropped at respective signal branchpoints on an optical transmission line out of signals of multiple channels amplified in an optical amplifier. The optical transmission system has an optical transmission line in which signals of multiple channels propagate, an optical amplifier provided on the transmission line, and a plurality of signal branchpoints disposed on the downstream transmission line in which the signals of the channels outputted from the optical amplifier propagate. Each of the signal branchpoints drops a signal of a channel with a lowest power level out of arriving signals in the channels. This reduces the dispersion of power levels among signals dropped at the respective branchpoints, as a whole of the optical transmission system.

Abstract: An optical device is provided, including two dual-fiber collimators, two single-fiber collimators, two filters connected respectively to the two dual collimators, and two mirrors. The two dual-fiber collimators are interconnected by coupling an optical fiber thereof to each other. One mirror is fixed in position, and the other mirror is mounted on a mechanism capable of moving up and down so as to switch an optical path.

Abstract: A communications network has a plurality of nodes interconnected by an optical transmission medium. The transmission medium is capable of a carrying a plurality of wavelengths organized into bands. A filter at each node for drops a band associated therewith and passively forwards other bands through the transmission medium. A device is provided at each node for adding a band to the transmission medium. Communication can be established directly between a pair of nodes in the network sharing a common band without the active intervention of any intervening node. This allows the network to be protocol independent. Also, the low losses incurred by the passive filters permit relatively long path lengths without optical amplification.

Abstract: The invention relates to an electro-optical module for transmitting and/or receiving optical signals on at least two optical data channels which are carried in an optical waveguide. The optical waveguide in the module forms at least two optical waveguide sections, with each section having at least one inclined end surface. The inclined end surfaces of the optical waveguide sections are positioned axially one behind the other. Light is injected into or light is output from the optical waveguide for a specific optical data channel by light for the optical data channel being passed to an inclined end surface, or emerging from it, at an angle to the optical axis of the optical waveguide.

Abstract: A filter module comprising a lens, three optical fibers, an optical filter, and a mirror, wherein the three optical fibers are arranged a single side of the lens.

Abstract: A WDM demultiplexer/multiplexer comprising a plurality of narrow band reflective filters linearly disposed along an optical axis, each narrow band reflective filter reflecting a single channel or group of channels and transmitting the remaining channels, is described. In a demultiplexing mode, an optical signal initially carrying channels at &lgr;1&lgr;2 . . . &lgr;N travels along the optical axis. Each narrow band reflective filter reflects a distinct channel and is tilted with respect to the optical axis such that it directs the reflected beam away from the optical axis to an output. Each narrow band reflective filter is substantially transparent to the remaining channels of the optical signal, such that the remainder of the optical signal proceeds along the optical axis substantially undisturbed.

Abstract: A communications network has a plurality of nodes interconnected by an optical transmission medium. The transmission medium is capable of a carrying a plurality of wavelengths organized into bands. A filter at each node for drops a band associated therewith and passively forwards other bands through the transmission medium. A device is provided at each node for adding a band to the transmission medium. Communication can be established directly between a pair of nodes in the network sharing a common band without the active intervention of any intervening node. This allows the network to be protocol independent. Also, the low losses incurred by the passive filters permit relatively long path lengths without optical amplification.

Abstract: The invention comprises a method and apparatus for implementing a relatively low cost add/drop multiplexer (OADM) wherein pre-demux and post-mux dispersion compensation is employed in a manner that substantially avoids imparting additional dispersion compensation to pass-through wavelength channels in a WDM system.

Abstract: An optical dropping apparatus and an optical add/drop multiplexer capable of dropping optical signals of an arbitrary wavelength from a WDM optical signal. The apparatus comprises a generating means for occurring four-wave mixing, a dropping means for dropping light of a predetermined wavelength, and a controlling means for controlling the wavelength of a pump light which is occurred four-wave mixing at the generating means. This apparatus is able to change the wavelength of the optical signals to be dropped, by changing the wavelength of the pump light.

Abstract: Improved designs of optical multiplexing/demultiplexing module are disclosed for use in multiplexing a composite optical signal into respective individual channels or wavelengths or demultiplexing individual channels or wavelengths into a composite optical signal. According to one embodiment, the optical multiplexing/demultiplexing module comprises an array of collimators, an array of optical filters and an array of mirrors. The collimators are boned to a common substrate after being aligned with a respect optical filter. Different from the prior art devices, the aligned positions of the collimators are secured or held up by preformed wedges. A bonding agent is then applied only to respective contacts between the collimators and the wedges. The wedges are further bonded to a common substrate to secure the collimators.

Abstract: A communications network has a plurality of nodes interconnected by an optical transmission medium. The transmission medium is capable of a carrying a plurality of wavelengths organized into bands. A filter at each node for drops a band associated therewith and passively forwards other bands through the transmission medium. A device is provided at each node for adding a band to the transmission medium. Communication can be established directly between a pair of nodes in the network sharing a common band without the active intervention of any intervening node. This allows the network to be protocol independent. Also, the low losses incurred by the passive filters permit relatively long path lengths without optical amplification.

Abstract: An add-drop filter, utilizing chiral elements, that enables a new signal to be added at a particular vacuum wavelength &lgr;′k to a fiber optic line carrying n signal channels over a band of wavelengths encompassing &lgr;1 . . . &lgr;k−1, &lgr;k, &lgr;k+1 . . . &lgr;n, while an existing signal, &lgr;k, is simultaneously dropped from the signal group.

Abstract: The wavelength tunable optical filter (1) comprises a resonant cavity (4) delimited by two opposite reflective elements (8, 8′) which are not wavelength selective, and a reflector (7) external to the cavity (4). The external reflector (7) exhibits transmission peaks for an integer number N of optical frequencies and the Fabry-Perot cavity (4) delimiting a phase tuning section (11) is sized so that the distance between the optical frequencies of any two resonant modes of the cavity (4) is never equal to the difference between the optical frequencies of any two transmission peaks of the external reflector (7).

Abstract: A collimator 111 for an input light, a collimator 112 for an output light, a collimator 113 for a branched light, a collimator 114 for an inserted light and a wavelength selecting filter 115 are provided on a common substrate 130, and mirrors 121 to 124 for correcting an optical path or prisms XXXX to XXXX capable of producing the same advantages are provided on the optical paths between the collimators 111 to 114 and the wavelength selecting filter 115 respectively. By adjusting the mirrors or prisms, the shift of the optical axis between the collimators is corrected.

Abstract: Disclosed herein is an optical device, terminal apparatus, and system for wavelength division multiplexing (WDM). The optical device includes a WDM port adapted to WDM, a specific port to which a specific wavelength substantially central of WDM channels is allocated, a plurality of first ports to which longer wavelengths are allocated, a plurality of second ports to which shorter wavelengths are allocated, and first to fourth optical filters. The first optical filter couples the WDM port to the second optical filter by the specific wavelength, and also couples the WDM port to the second optical filter by the other plural wavelengths. The second optical filter couples the first optical filter to the third optical filter by the longer wavelengths, and also couples the first optical filter to the fourth optical filter by the shorter wavelengths. The third optical filter couples the second optical filter to the first ports, and the fourth optical filter couples the second optical filter to the second ports.

Abstract: An optical system includes an optical frequency discriminator having a light source of an optical input beam, and an optical bandpass filter having a bandpass filter range and the optical input beam incident thereon at a bandpass-filter angle of incidence and may be desirably be adjusted. The optical bandpass filter transmits a first transmitted beam of a bandpass-filter frequency band and reflects a first reflected beam. An optical second filter has an optical edge in the bandpass range of the bandpass filter and the first reflected beam incident thereon at a second-filter angle of incidence. The optical second filter transmits a second transmitted beam band and reflects a second reflected beam.

Abstract: This invention provides a system that combines a wavelength multiplexer with an FM discriminator for chirp reduction and wavelength locker in a filter to produce a wavelength division multiplexed signal with reduced chirp. A partially frequency modulation laser signal is converted into a substantially amplitude modulation laser signal. This conversion increases the extinction ratio of the input signal and further reduces the chirp. A wavelength division multiplexing (WDM) method is used for transmitting high capacity information through fiber optics systems where digital information is carried on separate wavelengths through the same fiber. Separate transmitters normally generate their respective signals that are transmitted at different wavelengths. These signals are then combined using a wavelength multiplexer to transmit the high capacity information through the fiber optic system.

Abstract: A narrow bandpass optical filter for use in a WDM communication minimizes the system bit rate error by providing a sufficiently broad passband with respect to the data transfer rate yet has a low group delay across the passband. The passband shape is optimized to have a single maximum in the center of the passband and continuously decreasing transmission there from so as to minimize dispersion in GD across the passband.

Abstract: An AOTF drive method for driving a plurality of AOTFs connected in tandem comprises: separating a plurality of RF signals in advance into a plurality of groups; batch-branching the RF signals of each group in accordance with the number of steps of the AOTFS; and batch-adjusting the phases of the individual branched RF signals. As a result, this makes it possible to reduce the number of phase shifters compared to the prior art while maintaining the effectiveness of suppressing beats in the AOTFs.