Abstract: A scanning method that saves time by reducing calculations performed in a scanner. The scanner has a housing, a transparent platform installed on the housing, a document positioned on the transparent platform, a scanning module, a calibration paper, a memory, and a processor. If an effective image range has been determined within a predetermined amount of time after the scanner is turned on, the effective image range will not be redefined before scanning the document.

Abstract: A system and method for efficiently performing a white balance operation preferably includes an electronic camera device that captures image data using a imaging device. A color manager may then convert the captured image data into perceptual color space data. The color manager may next create a histogram of chromaticity vectors corresponding to pixels from the perceptual color space data. The color manager may then derive a neutral core vector corresponding to a neutral core peak from the histogram. The color manager may advantageously utilize the neutral core vector to identify a scene illuminant corresponding to color channel amplifier gains, and may then adjust the captured image data with the color channel amplifier gains to thereby complete the white balance operation.

Abstract: The purpose of the present invention is to provide an image processing apparatus which reproduces color characteristics close to target color characteristics as a whole while a high luminance color reproduction gamut of an image output apparatus is efficiently used.

Abstract: A method for saving and searching image adjusting parameter used in the saving and searching the contrast, brightness, and gamma adjusting parameter of digital image; wherein the parameter values are arranged in order into a plurality of memory address, and the critical values which are the minimum and the maximum of the output parameter range corresponsive to each of the input parameter, are saved in order into each of the foregoing addresses, thereby after the input parameter for the image adjustment is input, the maximum or minimum value in the corresponding input parameter range obtained from half of the memory address of the maximum output parameter value is compared with the foregoing input parameter value, and then repeat the binary search by this method until the matched range of memory address of the input parameter is searched, and further the corresponding output parameter of the image adjustment is obtained.

Abstract: When memory card MC is inserted into slot 34, control circuit 30 of color printer 20 obtains image output control information GI from memory card MC and analyzes it. When auto light source is not set as the light source, CPU 31 references the reference values and coefficients for the characteristics parameters except for color balance and then performs correction, and then adjusts the image data image quality to reflect the post-correction characteristics parameters. As a result, it is possible to automatically adjust the image quality of image data without losing the selectively set output conditions.

Abstract: A resonator system is disclosed for use in illuminating a diffractive element. The system includes a source of an electromagnetic field having a wavelength of &lgr;, and first and second optical elements, each of which is at least partially reflecting.

Abstract: A method for monitoring diffraction while recording a hologram includes: generating a source beam; generating a data beam by projecting a first component of the source beam through a data source, the data beam having a first polarization; generating a reference beam by adjusting a polarization of a second component of the source beam to provide a second polarization; recording a hologram in a holographic medium from an interference between the data beam and the reference beam; and measuring an offset component in an output arm of the data beam.

Abstract: An method for stabilized photonic transmission is described. A light source of limited coherence length is wavelength shifted, stabilized, and data encoded to provide a stabilized photonic signal. A modulation synthesizer provides a modulation waveform embedded with the shifting, stabilization and data encoding mechanisms. A variety of modulation techniques are supported. The modulation waveform is optimized for the particular modulation technique. A wavelength error detector provides feedback to the modulation synthesizer. The error signal is used to stabilize the photonic signal and correct channel wavelength errors. Fixed wavelength channels and spread spectrum channels are supported.

Abstract: An optical channel monitor is described, the optical channel monitor includes an optical input port, a photodetector disposed in an optical path communicating at least intermittently with the optical input port, an optical filter disposed in the optical path between the optical input port and the photodetector, and an optical band splitter disposed in the optical path between the optical filter and the photodetector. The optical filter is a multibandpass filter, such as a scanning Fabry-Perot filter. The optical channel monitor also comprises a reference light system for providing a calibration standard against which an optical signal input through the input port may be compared. The channel monitor finds application in optical transmission systems including wavelength division multiplexed (WDM) optical communication systems.

Abstract: A method of making an optical transmission system safe, the system including a transmission optical fiber and emitting an optical wanted signal, transmitting a transmitted optical signal containing the wanted optical signal and optical noise, sampling a portion of the transmitted optical signal constituting a monitoring optical signal, and analyzing the power of the monitoring optical signal to deduce, as a function of the power of the monitoring optical signal, whether the transmission optical fiber is broken. The method isolates in the monitoring optical signal a first signal containing only the noise and a second signal containing the noise and the wanted signal and compares the power of the first and second signals and to deduce that the transmission optical fiber is broken if the ratio of the power of the second signal to the power of the first signal is substantially equal to 1.

Abstract: A system and apparatus for photonic switching combines photonic add/drop multiplexing capabilities with photonic cross-connect switching capabilities. The photonic switch is coupled to a number of incoming fibers and to a number of outgoing fibers. Each incoming fiber is fed into a demultiplexer that demultiplexes the incoming optical signal into its component optical data streams. The demultiplexed optical data streams from each incoming fiber are fed into a corresponding drop-only fabric, which, for each demultiplexed optical data stream, either drops or passes the optical data stream. The passed optical data streams from the various drop-only fabrics are fed into a number of input ports of a photonic cross-connect switch. The photonic cross-connect switch switches each optical data stream from an input port to an output port. The signals from a number of output ports are combined to form an outgoing optical signal, which is sent over an outgoing fiber.

Abstract: A method and apparatus for determining a shortest path between a source node and a destination node in an optical network of nodes interconnected with optical transmission links is disclosed. A wavelength graph is used to represent an optical network as a set of electronic nodes and optical channel nodes corresponding to the network nodes with a set of internal links and optical channel links. The electronic node represents the electronic switching fabric that interconnects OEO equipment within a physical node. A single-source shortest path algorithm (e.g., Dijkstra's algorithm) is applied to the wavelength graph to determine a shortest path. The transformation of the network representation to include the electronic node greatly reduces the number of links in the wavelength graph and significantly increases the computational efficiency.

Abstract: In an optical signalling system, simultaneous signals are circulated on a looped path and fed out sequentially to a tuneable receiver. Conversely, sequential signals may be buffered in the loop and fed out simultaneously to a number of receivers. The system is suitable for use in a passive optical network employing wavelength-dependent routing, terminals transmit request packets (requesting a data transmission slot) in a common signalling time slot. Different delays are then applied to packets on different wavelength channels, allowing a number of request packets to be processed in sequence by a single optical receiver at the network controller.

Abstract: A versatile, wavelength-slicing methodology, referred to herein as spectrum division multiplexing (SDM), provides new avenues and technologies for optical communication applications. Specifically, SDM separates a composed optical signal into a group of output spectra. Each output spectrum carries a multiple of optical communication signal channels. The bandwidth of each channel and spacing between adjacent channels may differ from one output spectrum to another. A critical building block of SDM technology is a spectrum filter with periodic passbands, referred to herein as an optical spectrum synthesizer (OSS). The cascade of OSS devices, the combinations of OSS with prior art components and modules, and other new devices to be used in conjunction with OSS, lead to new spectrum devices that add new dimensions to existing and new optical network architectures. The invention of OSS leads to new Spectrum Division Multiplexing and management devices based on cascading OSS devices.

Abstract: Internal communication signals in a stored program controlled system comprising a plurality of units configured to process signals are provided by an optical beam line which is proximal to all of the plurality of units. The system of this invention uses Wavelength Division Multiplexing techniques to provide a plurality of logically independent subchannels over a single shared free space optical beam line.

Abstract: A method of coordinating channel power information in a wavelength division multiplexed (WDM) optical communication system is disclosed. The method determines weighting values for each channel of the WDM signal based on channel launch powers. A source data object may used to transmit the channel weights and channel information from network elements having channel sources such as transmitters to downstream network elements. Block data objects may be used to identify channel blocks in the system and are also transmitted downstream. The source and block objects may be correlated to determine which channels are in-view at a particular point in the network and thereby determine which of the channel weights should be used as a basis for managing the network at that point. A WDM system is also disclosed which may actively control channel launch powers and feed the adjusted launch powers into the method of coordinating channel power information.

Abstract: The present invention provides an optical wavelength multiplexing transmission apparatus and an optical output control method for an optical wavelength multiplexing transmission apparatus in an optical wavelength multiplexing transmission system using a main signal light and an OSC light. The optical wavelength multiplexing transmission apparatus (10a) is made up of a first transmitting/receiving section (52a) a second transmitting/receiving section (52b) and an apparatus supervisory control unit (54). This can not only achieve quick restoration from troubles, but also stably calculate an optical output level even if a change of the number of wavelengths to be multiplexed takes place in a main signal light, and even save troublesome adjustments for the improvement of reliability of a transmission line while eliminating the need for a signal source for the adjustment of a receive optical level at the initial installation.

Abstract: A tunable, reconfigurable optical add/drop multiplexer comprises a first signal routing component and at least one wavelength selective switch having an input port and an output port. The input port is optically coupled to the first signal routing component. The wavelength signal selective switch is wavelength tunable, so as to allow a selected wavelength to be routed to the first signal routing component and the rest of the wavelengths to be routed to the output port. According to an embodiment of the present invention the first signal routing component is an optical circulator.

Abstract: Internal communication signals in a stored program controlled system comprising a plurality of units configured to process signals are provided by an optical beam line which is proximal to all of the plurality of units. The system of this invention uses Time Division Multiplexing techniques to provide a plurality of logically independent subchannels over a single shared free space optical beam line. The single logical beam is divided temporally among the subchannels, with each subchannel operating for a selected timeslot or timeslots.

Abstract: An optical time-division multiplexer branches input light into a plurality of optical paths with different optical lengths. At least one path includes a section of optical fiber with an optical length that is adjustable by, for example, physical stretching. The input light is separately modulated on each optical path, and the modulated light signals are recombined into a multiplexed output light signal. Adjustment of the optical length of the optical fiber can compensate for changes in input wavelength and adjust the phase of successive pulses in the multiplexed output signal to provide a &pgr;-radian shift that enables long-haul optical transmission.

Abstract: A method and an apparatus for switching channel connection between multiple optical channels synchronously and automatically. The apparatus employs an optical switch to interface among a plurality of optical channels, and an optical power meter to monitor data transmission over the plurality of optical channels by measuring the optical power level of optical signals over the channel. When signal transmission is detected over a specific optical channel, the optical switch is locked to the specific optical channel allowing data signals over the specific optical channel to be transmitted to a specific device or another optical channel through the optical switch. When no optical signal is detected over the channel, said optical switch will be switched to another optical channel, such that signal monitoring and switching channels among a plurality of optical channels is able to be performed synchronously and automatically.

Abstract: The present invention discloses an interface circuit for a fiber transceiver, comprising: an encoder, for receiving and encoding an input data into an output differential signal; a comparator, for receiving an input differential signal from the fiber transceiver and generating an input signal; a decoder, for receiving the input signal and generating an encoded signal and an input data; and a detector, for receiving the encoded signal and generating a link signal supplied to the decoder to generate the input data.

Abstract: Network for transmitting and using electromagnetic radiation for two or more functionally different useful purposes. Such a network may be comprised of a signal source apparatus to provide information, an electromagnetic radiation generator capable of being modulated for providing electromagnetic radiation, electronic circuitry for modulating the electromagnetic radiation generator, medium through which the electromagnetic radiation passes and is transmitted, a receiver apparatus for receiving and demodulating the modulated electromagnetic radiation, a first user means for processing and making use of the information to achieve a useful functional purpose, and second user means for achieving a useful functional purpose from said radiation said useful functional purpose being different from the purpose of said first user means.

Abstract: A system comprising a solid-state optical beam regulator, an optical sensing device, and a computer provides for fast, accurate, and automatic tracking, steering, and shaping of an optical beam, such as that required in free-space optical communications. With a CMOS imager as the sensing device and a regulator constructed of a stress-optic glass material whose index of refraction is altered by induced stress, the system can track beam perturbations at frequencies greater than 1 kHz. This performance makes the system suitable for a variety of applications in free-space optical communications.

Abstract: A chromatic dispersion characterization system for an optical transmission path is based on setting the operating point (the DC bias) of an external modulator alternatively on the inverting and non-inverting characteristic of the modulator. A dispersion regime of choice may be selected based on the modulator's alpha parameter, and the BER information recorded against the respective values of the DC bias. This system can be used to determine when the net CD in a link is zero, i.e. the network provider has provisioned sufficient compensation to match the CD in the link. The link operates in a zero-dispersion regime when the quality of the received signal does not change between the two modes.

Abstract: Internal communication signals in a stored program controlled system comprising a plurality of units configured to process signals are provided by an optical beam line which is proximal to all of the plurality of units. The beam line is configured to contain optically encoded signals, which comprises signals transmitted between and/or among the plurality of units. Each unit includes a probe for injecting optically encoded signals in the beam line and/or and for receiving optically encoded signals from the beam line. Processing units include at least one aperture for passage of the beam line. Processing units may also include a movable portion that is moved during installation of the processing unit and then replaced after the main body is in place.

Abstract: Internal communication signals in a stored program controlled system comprising a plurality of units configured to process signals are provided by a free space optical beam line which is proximal to all of the plurality of units. The free space beam line is configured to contain optically encoded signals which comprises signals transmitted between and/or among the plurality of units. Each unit includes a probe for injecting optically encoded signals in the free space beam line and/or and for receiving optically encoded signals from the free space beam line. Advantageously, there may be a first terminal at a first end of the beam line to configure to transmit and terminate the optically encoded signals and a second terminal unit at the second end of the free space beam line configured to transmit and terminate the optically encoded signals.

Abstract: A free-space optical communication system serves transmit/receive subscriber terminals. Each subscriber terminal includes a photo-detector and one or more sources of modulated radiation. A base terminal comprises sources of modulated optical radiation intended for the subscriber terminals and a receiving system for receiving modulated radiation from the subscriber terminals. At the base terminal, and preferably at each subscriber terminal, each source has an associated beam shaping device. The receiving system includes photo-detectors and a shared wide-angle objective implemented as a single lens. Within the base terminal, the objective lens is optically coupled only to the photo-detectors of the receiving system, and the beam shaping devices at that terminal do not have common optical elements with the lens or with each other.

Abstract: An optical communication system for optically transmitting transmission data from a transmitting station to a transmitting device includes an adder for adding an intermediate frequency subcarrier signal modulated with data to be transmitted to a pilot carrier signal as a sinusoidal wave, and an electro-optical converter for electro-optically converting the above sum signal to an optical signal by directly modulating a semiconductor laser element having a resonant frequency fr in accordance with the sum signal and transmitting the signal to an optical fiber for a down link.

Abstract: There is disclosed an optical transmission system ensuring high-quality monitor control even if an optical fiber fault occurs. A monitor instruction sending unit sends a monitor instruction. An operating condition recognizing unit receives a response signal and recognizes the operating condition. A filtering unit filters the monitor instruction and the response signal. A monitor control unit monitors the operating condition of its own repeater in response to the monitor instruction, and generates resultant response information. A pump unit generates a pump light to cause Raman amplification within an optical fiber transmission medium. A regeneration control unit performs a regeneration control of the response signal to thereby create a regenerated signal. A modulation control unit modulates the pump light by the response information or the regenerated signal to thereby generate the response signal.

Abstract: An emitter of optical signals for optical fibers includes an electroabsorption modulator downstream of a laser and a Mach-Zhender modulator downstream of the electroabsorption modulator and controlled by at least one clock to eliminate for each pulse of the resulting signal from the first modulator a portion of signal in a time range including the rising edge and in a time range including the falling edge.

Abstract: To provide an optical transmitter in which reduced power consumption is achieved by, when a signal generator needs data transmission, driving a laser emitting device to perform emission. An optical transmitter 1 includes a receiver 11, a laser driving circuit 12, a light emitting unit 13 constituted by a plurality of laser emitting devices, and an EDID memory 14. The receiver 11 and the laser driving circuit 12 are supplied with power from a dedicated external power supply V1 through a power-supply line 15, and the power-supply line 15 is provided with a switch 16. The contact of the switch 16 is controlled to open and close based on a power-supply voltage supplied from the DDC controller 23 to the EDID memory 14.

Abstract: An optical transmission system comprising transmitter, link and receiver. At the receiver a decoder is connected to receive the encoded optical signal from the link and decode it according to a decoding signature carried by the decoder that is complementary to the encoding signature at the transmitter coder. The signal is thus decoded to produce a decoded optical signal having a broadened autocorrelation peak and an unwanted background pedestal component. After amplification (EDFA3) the decoded signal is supplied through a non-linear optical element in the form of a non-linear optical loop mirror (NOLM). The NOLM enhances the autocorrelation peak intensity relative to the pedestal and compresses its pulse width, to return the pulse width to the same or narrower than prior to coding at the transmitter.

Abstract: Provided is an actuator for scanning detecting light, comprising an optical element for emitting detecting light, a moveable part supporting the optical element, a sheet spring having a fixed end and a moveable end supporting the moveable part; and drive means for driving the moveable part so as to scan the detecting light. Thus, a spring-mass system is formed in which the moveable part retaining the optical device acts as the mass, and the first order resonant frequency of the system may be selected so as to be higher than the operating frequency (scanning frequency). A bearing for a sliding part is not required, and the resistance loss can be thereby eliminated. These factors contribute to a favorable responsiveness. Also, by properly designing the sheet spring, a lighter and more compact design is enabled than would be possible with the conventional arrangement.

Abstract: A light modulator includes elongated elements arranged parallel to each other and suspended above a substrate. The light modulator operates in a first diffraction mode and in a second diffraction mode. In the first diffraction mode, an incident light diffracts into at least two diffraction orders. In the second diffraction mode, the incident light diffracts into a single diffraction order. Each of the elongated elements comprises a central blazed portion, a first outer blaze transition, and a second outer blaze transition. The central blaze portion couples the first outer blaze transition to the second outer blaze transition. Each of the central blazed portions comprises a reflective surface. Selected ones of the central blazed portions comprise a first conductive element. The first outer blaze transition and the second outer blaze transition are coupled to the substrate. The substrate comprises a second conductive element.

Abstract: A system for the production of a dynamic image for use in display applications includes a light source (16) which travels via a liquid crystal modulator (18) placed in the path of the light source (16). The output of the LC modulator (18) passes modulated light a lens ray (22) which itself guides light to an optically addressed spatial light modulator (24). The resulting real image from the optically addressed spatial light modulator (24) may be used in two dimensional and three dimensional displays. The addressing frame-rate of the liquid crystal modulator (18) is substantially greater than the frame-rate of the optically addressed spatial light modulator (24).

Abstract: In order to provide comprehensive and multi-purpose security, an optical security device comprises a substrate (10), and at least a first optically structured layer (14) which is such as to provide first, second and third optical inspection levels, namely a first inspection level (2) where a first optical property can be discerned with the naked eye, a second level (4) in which an object can be discerned with the aid of an optical inspection tool (26), and a third level (6) in which an encrypted object can be discerned with a decrypting optical inspection tool (20). The first layer (14) is constructed as a retarder plate of LCP material, having an array of elemental areas having different predetermined orientations.

Abstract: A method of making a micromirror unit is provided. In accordance with the method, a micromirror unit is made from a material substrate having a multi-layer structure composed of silicon layers and at least one intermediate layer. The resulting micromirror unit includes a mirror forming base, a frame and a torsion bar. The method includes the following steps. First, a pre-torsion bar is formed by subjecting one of the silicon layers to etching. The obtained pre-torsion bar is rendered smaller in thickness than the mirror forming base and is held in contact with the intermediate layer. Then, the desired torsion bar is obtained by removing the intermediate layer contacting with the pre-torsion bar.

Abstract: An optical switch element is described, which includes a fixed layer disposed outwardly from a substrate and a movable mirror assembly disposed outwardly from the fixed layer. The moveable mirror assembly is operable to move relative to the fixed layer responsive to a voltage applied to the movable mirror assembly. In a particular embodiment, the movable mirror assembly includes an inner strip spaced apart from the fixed layer by a first distance and an outer strip disposed approximately adjacent to the inner strip and spaced apart from the fixed layer by a second distance which is greater than the first distance. The optical transmission of the optical switch element changes depending on the position of the movable mirror assembly.

Abstract: An optical switch element is described, which includes a fixed layer disposed outwardly from a substrate and a movable mirror assembly disposed outwardly from the fixed layer. The moveable mirror assembly is operable to move relative to the fixed layer responsive to a voltage applied to the movable mirror assembly. In a particular embodiment, the movable mirror assembly includes an inner strip spaced apart from the fixed layer by a first distance and an outer strip disposed approximately adjacent to the inner strip and spaced apart from the fixed layer by a second distance which is greater than the first distance. The optical transmission of the optical switch element changes depending on the position of the movable mirror assembly.

Abstract: The current invention is directed to devices and systems with patterned reflective surfaces. The reflective surfaces are patterned with primary reflective regions and gap regions. The gap regions provide for separation between reflective material within adjacent primary reflective regions. The separation between reflective material reduces atomic flux which can lead to the depletion of the reflective material within regions of the reflective surface that are exposed to an intense light source. The primary reflective regions are preferably formed from a reflective material such as aluminum, silver, gold or platinum. The gap regions are left vacant or deposited with second material which is non-reflective, reflective or semi-reflective. The patterned reflective surface is preferably formed on a micro-structure, such an elongated ribbon. The patterned ribbon structure is preferably one of a plurality patterned ribbon structures in a grating light valve device.

Abstract: An optical modulator having an optical modulator window coupled to a substrate and a method of manufacture thereof. In one embodiment, the optical modulator includes at least one drive electrode that adjusts a portion of the optical modulator window to attenuate light passing therethrough. The optical modulator further includes a sense element configured to measure a characteristic associated with the optical modulator window.

Abstract: A light modulation element is constituted as a light modulation element for constituting a GLV device, and has the same constitution as the conventional light modulation element except for differing in the structure of a combined light reflective film and membrane-side electrode of a membrane. The combined light reflective film and membrane-side electrode is composed of a two-layer metallic film forming a TiN film of 10 nm to 70 nm in thickness provided as a lower layer, and an Al film of 50 nm to 150 nm in thickness provided thereon. In the combined light reflective film and membrane-side electrode, the Al film has a smooth reflective surface and a high light reflectance, so that the light utilization efficiency of the light modulation element is high.

Abstract: The present invention relates to an improved EPD which comprises the in plane switching mode. More specifically, the EPD of the present invention comprises isolated cells formed from microcups of well defined size, shape and aspect ratio and the movement of the particles in the cells is controlled by the in-plane switching mode. The EPD of the present invention may be produced in a continuous manufacturing process, and the display gives improved color saturation.

Abstract: This invention relates to an electrophoretic display comprising isolated cells of well-defined shape, size and aspect ratio which cells are filled with charged pigment particles dispersed in a solvent, a backlight and optionally a background layer. The display may have the traditional up/down switching mode, an in-plane switching mode or a dual switching mode.

Abstract: An object of the invention is to provide an acousto-optic tunable filter (AOTF) that realizes filter characteristics where the wavelength characteristics in the vicinity of a selected center wavelength are smooth, and the bandwidth thereof is sufficiently narrow. To this end, an AOTF of the invention has a construction where a mode coupling section and a wavelength characteristic flattening section provided with an optical filter configuration for selecting an optical signal based on mode conversion using the acousto-optic effect, are respectively connected via a mode branching device. The mode coupling section mode converts an optical signal corresponding to a selected wavelength, and the wavelength characteristic flattening section again mode converts only the optical component of a part of the selected optical signal mode converted in the mode coupling section in the vicinity of a center wavelength thereof.

Abstract: Wavelength conversion apparatus is described that utilizes a Kerr cell to modulate the polarization of a pump laser beam having a first wavelength before the beam is input to a optical parametric oscillator/amplifier wavelength converter to generate a laser beam having a second wavelength. By modulating the polarization of the pump laser beam using the Kerr cell, the optical wavelength converter can be controlled to switch on and off or otherwise amplitude modulate the second wavelength laser beam output from the converter, and to correspondingly amplitude modulate the first wavelength and all other laser beams being output from the converter. In addition, with the pump laser beam and the second wavelength laser beam always being output from said wavelength converter there is a substantially constant thermal load on said wavelength converter creating substantially constant thermal lensing in the wavelength converter crystal that may be easily compensated using optical means.

Abstract: A pump assembly includes a pump source operable to generate at least one pump signal operable to pump a Raman gain medium of a Raman amplification stage. The pump assembly further includes an active gain equalization element operable to manipulate a wavelength or an intensity of the at least one pump signal to affect a spectral shape of a Raman gain spectrum associated with the Raman amplification stage. In one particular embodiment, the combination of the Raman gain spectrum and a substantially non-uniform gain spectrum of an existing amplification stage over a wavelength range &lgr;s results in a substantially uniform overall gain spectrum over a wavelength range of at least &lgr;s.

Abstract: A method and apparatus for dynamically obtaining a substantially linear gain tilting of the output spectrum of an EDFA, in either automatic gain control or automatic power control modes. A necessary tilt is obtained while holding the total gain or total output power of the EDFA constant. The apparatus includes a variable mid-stage attenuator inserted between two (first and second) gain sections of the EDFA. The tilting is performed by ordering the attenuator to increase or decrease its attenuation in a value proportional to the tilting needed, while changing substantially simultaneously the pumping of the second gain section. The attenuation change process is based on the saturation mechanism of the erbium amplifier in the L-band, which translates the wavelength-independent loss of a variable optical attenuator into a linear wavelength-dependent gain at the EDFA output.

Abstract: The present invention utilizes an amplified spontaneous emission (ASE) as a pumping source, thereby enhancing an amplification capability of a two-stage L-band EDFA. The two-stage L-band EDFA of the present invention includes a first amplifier and a second amplifier. The first amplifier is designed as a reflective amplifier, thereby re-amplifying a forward ASE by means of a gain medium. The first amplifier has a pumping LD, a WDM coupler, a first EDF and a Faraday rotating mirror. The second amplifier plays a role in amplifying an optical signal by utilizing the re-amplified forward ASE and the backward ASE as the pumping light. Here, the forward ASE and the backward ASE are transmitted to the second amplifier through an optical circulator. The second amplifier has a second EDF and an optical isolator.