Abstract: The proposed amplifier structure and associated method of optical signal amplification efficiently utilizes the limited length of rare earth-doped optical amplifier. A multi-stage of amplification stages, which includes a first erbium-doped fiber amplifier stage pumped by a first pump light source and a second erbium-doped fiber amplifier stage pumped by a second pump light source, is provided and includes a split section disposed between the first and second amplification stages for splitting the amplified signal light into a C-band and a L-band; a reflector for reflecting the amplified output of the second amplifier stage back into the second amplifier stage and the first amplifier stage in a reverse direction; a combiner for combining the reflected output, in succession, from the second amplifier and first amplifier to produce an output signal; and, a circulator for redirecting the reflected output traveling in a reverse direction to the input of the combiner.

Abstract: An optical amplifier with improved output power utilizing less optical fiber components and reduced noise is disclosed. A first optical fiber amplifier is pumped by a first light source prior to splitting into a number of sub-bands, and a second optical fiber amplifier is pumped by a second light source. One of the sub-bands is amplified in multiple stages using a reflector, by passing the amplified sub-band back into the second optical amplifier in a reverse direction. Thereafter, all amplified sub-band signals are recombined to produce an output signal.

Abstract: An optical amplifier to reduce signal loss by reducing crosstalk, and method therefor. A demultiplexer isolates an optical signal into a first wavelength band and a second wavelength band. The first and second wavelength bands are separately amplified in first and second optical amplifiers, respectfully, first and second optical amplifies each including cutoff filters to cutoff the wavelength band not corresponding to the particular amplifier. Optical receiving elements monitor light input to the first and second optical amplifiers and receive crosstalk signals on an output side.

Abstract: A method and apparatus for amplifying an optical signal is provided. In accordance with one example embodiment of the invention, the optical amplification system includes an optical signal traveling through the system. At least one module of the optical amplification system is suitable for one of selectively separating and combining one or more individual sub-bands of the optical signal. At least one amplifier is disposed to separately amplify each of the one or more individual sub-bands.

Abstract: Wideband optical amplifiers that use two parallel amplifiers in different operating spectral ranges and two different or identical sampled Bragg gratings as the channel splitter and combiner.

Abstract: An optical system for producing high power laser beams has an in/out coupler for receiving an input laser beam from an oscillator. The coupler inputs the beam to a first multiplexer which produces a plurality of beams which are sent to a plurality of fiber amplifiers. A second beam multiplexer receives the thus amplified plurality of beams to combine then into a single amplified beam which is input to a loop PCM (phase conjugate mirror). A multi-mode fiber amplifier is included in the loop PCM. The output of the loop PCM is phase conjugated with the amplified beam input to the loop PCM thereby eliminating any phase and polarization distortions and aberrations occurring in the fiber amplifiers. The output of the loop PCM is supplied in reverse direction through the second multiplexer, the fiber amplifiers and the first multiplexer in that order and then through the in/out coupler as a high power output laser beam.

Abstract: An object of the invention is to provide, for an optical amplifier which performs amplification of optical signals of two wavelength bands, an optical amplifier and an optical amplification method of a simple configuration which can deal with restrictions on installation space, power consumption and the like. Hence with the optical amplifier of the invention, optical circulators are respectively connected to opposite ends of an optical amplifying means, and optical signals of the respective wavelength bands of a first wavelength band and a second wavelength band are input and output to the optical amplifying means via each of the optical circulators so that the propagation directions of the respective optical signals of the respective wavelength bands are in mutually opposite directions inside a rare earth element doped fiber. As a result, the optical signals of the respective wavelength bands can be collectively amplified with a simple configuration using a single rare earth element doped fiber.

Abstract: The present invention provides tunable optical system, and a method for forming the same, that exhibits a broader tuning range with fewer components than prior art tunable optical systems. The tunable optical system of the present invention includes a plurality of wavelength routers, each having a different optical channel resolution, optically coupled to a plurality of optical amplifier arrays. The free spectral range of each of the second and subsequent wavelength routers is equal to a total bandwidth of one of its respective grating orders. The system is tuned by selectively activating optical amplifiers in each of the optical amplifier arrays. The tunable optical system of the present invention can be used to make tunable semiconductor emitters, receivers and filters.

Abstract: A laser transmitter capable of transmitting large numbers of WDM channels but requiring locking of only a single channel. Each of the channels can be individually modulated using an external modulator.

Abstract: A very low noise figure optical amplifier is provided which includes a noise reduction apparatus as part of the structure of the optical amplifier. To improve the signal-to-noise ratio (SNR) of the amplified optical signal, the noise reduction apparatus makes use of the coherence of a coherent component of an amplified optical signal having a coherent signal power and the incoherence of an incoherent component of the amplified optical signal having an incoherent signal power. The amplified optical signal is split in two path signals with each path signal having the same intensity but a different phase. The optical path length the path signals is selected such that coherent path components are combined constructively at a main output while the power of the incoherent path components is divided between the main output and at least one subsidiary output. The result is an increase in the SNR, and a decrease in noise figure (NF) of approximately 3 dB.

Abstract: An optical amplifier for two adjacent bands of optical data channels provides gain across the entire spectrum, including the so-called dead-band, by splitting the entire input signal equally into two paths. One path is optimized to amplify one band and the other path is optimized to amplify the other. An optical delay in one path, usually the one optimized for the lower wavelength band, ensures equal optical path lengths for the two paths. The amplified signals in that two paths are then combined to yield or flat gain profile across the two bands and the gap in-between.

Abstract: In the optical amplifier an optical divider based on long wavelength (or short wavelength) transmission type dielectric multi-layer filter divides input signal light according to wavelengths, and amplifying sections disposed in parallel and having different respective wavelength amplification regions respectively amplify light signals emitted from the optical divider, and an optical combiner based on long wavelength (or short wavelength) transmission type dielectric multi-layer filter combines light signals output from the respective amplifying sections. In another configuration of the optical amplifier, input signal light is divided using an optical divider based on a dielectric multi-layer filter of a long wavelength (or short wavelength) transmission type, and output signals from the divider are filtered using an optical filter connected in series to a short wavelength (or long wavelength) amplifier generating a loss in the long wavelength (or short wavelength) region of the light signals.

Abstract: The present invention discloses a wide band optical amplifier with a common mid-stage device. In the wide band optical amplifier according to the present invention, the signals that enter the amplifier are first split into a couple of sub-band signals. The sub-band signals are amplified independently at different optical amplification sections, but they share a common mid-stage device, which reduces the complexity and the cost of the amplifier. The sub-band signals propagate count-directionally in the common mid-stages device to reduce the nonlinear interactions between the signals in different sub-bands. A wide band optical amplifier incorporating a common mid-stage device with directionality is also disclosed.

Abstract: A method and apparatus for amplifying an optical signal is provided. In accordance with one example embodiment of the invention, the optical amplification system includes an optical signal traveling through the system. At least one module of the optical amplification system is suitable for one of selectively separating and combining one or more individual sub-bands of the optical signal. At least one amplifier is disposed to separately amplify each of the one or more individual sub-bands.

Abstract: An optical amplifier for a 4-fiber system having two inputs and outputs is provided that makes use of a single amplifier rather than two separate amplifiers. The optical amplifier node makes use of an interleaver before and after the single amplifier to demultiplex and multiplex even and odd channel signals traveling in opposite directions. The arrangement can also amplify wide channel spaced signals traveling through a plurality of optical fibers. The optical amplifier node can be combined with other like amplifier nodes to provide more complex amplifier solutions at reduced costs due to the need for only half of the typical number of amplifiers. The optical amplifier node can also be combined with, e.g., variable optical attenuators, L/C/S filters, channel add/drop, co- and counter-propagating Raman amplification, and dispersion compensation modules to modify the optical signals as desired.

Abstract: An apparatus is provided including a source of spectrally dispersed seed wavelengths optically coupled to an array of fibers. Laser diode pumps are optically coupled to the array of fibers for amplifying the wavelengths through the array. A computer controlled feedback loop intercouples the array of fibers and laser diode pumps, the source of seed wavelengths and/or phase modulators for maintaining the wavelengths and relative phases in the array of fibers to desired levels. A compressor is optically coupled to an end of the array of fibers so as to receive and overlap the wavelengths from the individual fibers of the array.

Abstract: The present invention relates to an arrangement and a method relating to optical channel equalizers. The channel equalizer includes at least one Q-port direction-dependent router (40), where Q≧3, one N-channel WDM (de)multiplexer (30), where N≧2, N-number of amplifying waveguides (31, 32, 33, 34, 35, 36, 37 and 38), at least N-number of fiber amplifiers (51, 52, 53, 54, 55, 56, 57 and 58), at least N-number of Bragg gratings (61, 62, 63, 64, 65, 66, 67 and 68), at least N-number of variable optical pump laser attenuators (71, 72, 73, 74, 75, 76, 77 and 78), at least one optical splitter (20 and 22) and at least one pump laser (10, 12, 14 and 16) per optical splitter (20 and 22). At least one of the ports (42, 44 and 46) on the direction-dependent router (40) is disposed on a first side of the WDM (de)multiplexer (30).

Abstract: A method and apparatus for amplifying the optical signals of a C-band (1550 nm wavelength band) and a L-band (1580 nm wavelength band) in a wide-band optical fiber amplifier, wherein the incoming optical signals are separated into the 1550 nm wavelength band and the 1580 nm wavelength band by a WVDM optical coupler and respectively amplified by a C-band EDFA and a L-band EDFA A backward ASE generated by the C-band EDFA is fed back to the L-band EDFA by a circulator as a supplementary pumping light to the amplification of the optical signals of the 1580 nm wavelength band.

Abstract: A wavelength-selective filter, such as a narrow bandpass filter, is used to filter both the input and output of an optical amplifier. The selected channel is amplified and can be re-combined with the other original channels or provided to another output, depending on amplifier configuration. In a particular embodiment, a two-stage amplifier with center stage access uses a single gain-flattening filter to compensate for gain tilt of both amplifier stages.

Abstract: A method and apparatus for treating tissue directs first and second wavelengths of energy, e.g., laser or ultrasonic signal energy, into an overlap region of tissue such that the first and second wavelengths mix in situ to form a third wavelength. The third wavelength effectively couples energy into the tissue to treat tissue in said overlap region, producing local heating or cavitation. Wavelengths may be selected such that overlying tissue is unharmed, and the two wavelengths may be applied along different paths and cross in the overlap region. Absorbers or dyes may be used to tailor absorbance of the third wavelength. When using ultrasonic energy, signals of several megahertz may be so mixed to provide a lower frequency treatment signal such as a 200 kHz treatment signal or a subharmonic. Laser signals may be mixed to form a treatment signal in the infrared.

Abstract: The present invention relates to a wavelength-multiplexed light amplifying apparatus to be used in a state of being connected to a branching portion of a multiplexing/branching unit or to be used for a m×n matrix optical switch of an optical cross-connect. The wavelength-multiplexed light amplifying apparatus is composed of a plurality of wavelength-multiplexed light amplifying units and an optical feedback loop system. A signal input port of an optical branching section in one wavelength-multiplexed light amplifying unit is connected to an output side of an optical amplifying section in the preceding wavelength-multiplexed light amplifying unit. This configuration disperses the power loss of an optical signal to perform amplification with high efficiency and further enables the expansion of the branching port in the in-service.

Abstract: Multiple function bandwidth management systems. Bandwidth-management systems for an optical network are easily assembled by concatenating a plurality of intelligent, miniaturized, bandwidth-management modules (BMM's) together. The BMM's subdivide the wide available spectrum into narrow band segments. Each individual BMM is designed to overcome loss and optimize dispersion, gain, and power or gain equalization for a few channels at a time. Each device includes optical connectors and filters, as well as any other components necessary to direct the band of optical channels through the device's optical path while passing other optical channels within the spectrum to additional devices which can be connected without disturbing existing bandwidth-management modules. Each BMM also includes a digital control module that operates the BMM in any one of a plurality of selectable operating modes.

Abstract: An optical waveguide optical amplifier device for use with an optical telecommunications system that transmits optically amplifiable subscriber channels and communicates service information internally within the system with optical service channels and includes an optical amplifier input, an amplifier output, and optical amplifier medium. The optical amplifier input includes a reflective isolator longitudinal body with a first end and a second end. The first end includes an input fiber for receiving the subscriber and optical service channels inputted into the amplifier input and an output fiber for transmitting the subscriber channels to the amplifier medium. The second end of the reflective isolator body includes an optical service channel accessor which guides the subscriber channels to the output optical fiber.

Abstract: Disclosed is an optical signal repeating and amplifying device which has: an optical amplifier which amplifies an optical signal to be input thereto and then outputs it; and an optical filter means through which only one wavelength light of the optical signal to be output from the optical amplifier is passed. Also disclosed is an optical level adjusting device which has: an optical demultiplexer which demultiplexes a wavelength-multiplexed optical signal into a plurality of wavelength lights; a plurality of optical attenuators which attenuate separately the demultiplexed plurality of wavelength lights to be output from the optical demultiplexer; and an optical multiplexer which multiplexes the attenuated wavelength lights to be output from the plurality of optical attenuators into a wavelength-multiplexed optical signal and output it.

Abstract: Amplifiers having multiple gain stages are provided. Some of the gain stages provide gain in a first wavelength band and some of the gain stages provide gain in a second wavelength band. The gain stages that provide gain in the first band are interleaved with the gain stages that provide gain in the second band. The gain stages may be based on rare-earth-doped fiber amplifiers, Raman-pumped fiber amplifiers, or other suitable optical amplifiers. Gain stages may be used that include parallel amplifier branches. Each of the parallel branches may handle a separate wavelength range.

Abstract: In an optical regenerator for use in an optical transmission system, an optical input signal to the regenerator comprising N wavelength division multiplexed channel signals is received in a signal synchronizing arrangement which synchronizes the phase of all of the N channels, where N·2. An optical output signal from the signal synchronizing arrangement has N phase-synchronized wavelength division multiplexed channels and is provided as an optical input signal to a nonlinear optical loop mirror (NOLM) arrangement. The NOLM has a high nonlinearity fiber loop that propagates equal parts of the optical input signal from the signal synchronizing arrangement in both a clockwise (CW) and a counterclockwise (CCW) direction. An optical clock signal from a laser having a phase that matches the phase of the CW and CCW propagating signals is multiplexed with the CW signal to provide a 180 degree phase shift between the CW and CCW propagating signals while propagating in the optical fiber loop.

Abstract: A method of broadband amplification divides an optical signal of wavelength of 1430 nm to 1620 nm at a preselected wavelength into a first beam and a second beam. The first beam is directed to at least one optical amplifier and produces an amplified first beam. The second beam is directed to at least one rare earth doped fiber amplifier to produce an amplified second beam. The first and second amplified beams are combined.

Abstract: A phase conjugate laser mirror employing Brillouin-enhanced four wave mixing allows multiple independent laser apertures to be phase locked producing an array of diffraction-limited beams with no piston phase errors. The beam combiner has application in laser and optical systems requiring high average power, high pulse energy, and low beam divergence. A broad range of applications exist in laser systems for industrial processing, especially in the field of metal surface treatment and laser shot peening.

Abstract: A method of broadband amplification divides an optical signal of wavelength of 1430 nm to 1620 nm at a preselected wavelength into a first beam and a second beam. The first beam is directed to at least one optical amplifier and produces an amplified first beam. The second beam is directed to at least one rare earth doped fiber amplifier to produce an amplified second beam. The first and second amplified beams are combined.

Abstract: An optical amplification apparatus for adjusting optical power of wavelength-multiplexed signal light at respective wavelengths and for adjusting the optical output power at the respective wavelengths and a deviation of the optical output power between the wavelengths. An optical power adjusting unit for receiving inputted light having signal light at a plurality of different wavelengths (&lgr;1, &lgr;2, &lgr;3, . . . , &lgr;N) multiplexed thereon, amplifying or attenuating light at least one wavelength included in the received light independently of light at different wavelengths from the wavelength of the light, is provided before or after an optical amplifier unit for amplifying the light having the signal light at the plurality of different wavelengths multiplexed thereon. Further, a control unit is provided for controlling the gain of amplification or attenuation performed by the optical power adjusting unit and the gain of amplification performed by the optical amplifier unit, respectively.

Abstract: An optical decision circuit, based on gain clamped semiconductor optical amplifiers, is disclosed. This optical decision circuit can be used for 2R signal regeneration in optical communication systems. By adding a clock signal to the input of said optical decision circuit, said circuit is also suited for 3R regeneration. Such a circuit can easily be implemented as an integrated circuit or an OEIC.

Abstract: A burst mode optical receiver using two amplifiers having different bandwidth. The receiver includes an optical coupler separating an input optical signal into two parts and outputting the same, a delay circuit formed of a first optical fiber delaying an optical signal packet outputted through the optical coupler by a half of packet duration and a second optical fiber passing the optical signal packet without delay, and a first pre-amplifier having a high bandwidth for receiving an optical signal from the first optical fiber and amplifying the same and a second pre-amplifier having a low bandwidth for receiving an optical signal from the second optical fiber and amplifying the same, for thereby improving a receiving sensitivity without using a preamble bit.

Abstract: A method and apparatus are provided for amplifying a first optical signal having a first wavelength and a second optical signal having a second wavelength. The method includes the steps of routing the first and second optical signal into a first and second optical amplifier coupled in parallel and amplifying the first optical signal at the first wavelength in the first optical amplifier and the second optical signal at the second wavelength in the second optical amplifier.

Abstract: The invention relates to a method for amplifying an optical signal and to an amplifier unit (OFA) to which an optical input signal comprising a plurality of wavelength channel signals each at its dedicated wavelength is supplied. In the method, (a) demultiplexing is carried out to separate each wavelength channel signal from the input signal, (b) a first multiplexing is carried out, combining each separated wavelength channel signal with a separate pump signal, (c) each combination of a wavelength channel signal and pump signal is guided to its dedicated amplifier means (FA1 . . . FA4), and (d) the pump signals are separated from the amplified wavelength channel signals obtained from the amplifier means and a second multiplexing is carried out, combining the amplified wavelength channel signals into an outgoing WDM signal.

Abstract: An optical amplifier assembly integrating wavelength selective input and output filters. Integration of wavelength selective filters with a doped fiber optical amplifier stage provides a modular amplifier for use in wavelength division multiplexed optical communication systems. In one embodiment, a center tap provides access to the selected light signal after a first amplifier stage, allowing signal modification before returning the light signal to a second amplifier stage of the integrated amplifier. In a further embodiment, a pump interconnect is provided between the first and second amplifier stages to allow operation of both amplifier stages from a single pump light source.

Abstract: A wavelength division multiplexed transmission system and a transmitting method using the same are provided. The wavelength division multiplexed transmission system includes a transmitting optical terminal station for transmitting a supervision channel, delaying a plurality of data channels by a predetermined time, and transmitting the delayed data channels, a plurality of wavelength division multiplexed optical amplifying portions for controlling amplification gain according to gain information included in the supervision channel and amplifying the delayed and incident data channels according to the controlled gain, and a receiving optical terminal station for receiving the supervision channel and the data channels output from the wavelength division multiplexed optical amplifying portion.

Abstract: The invention relates to a method for amplifying an optical signal and to an amplifier unit (OFA) to which an optical input signal comprising a plurality of wavelength channel signals each at its dedicated wavelength is supplied. In the method, (a) demultiplexing is carried out to separate each wavelength channel signal from the input signal, (b) a first multiplexing is carried out, combining each separated wavelength channel signal with a separate pump signal, (c) each combination of a wavelength channel signal and pump signal is guided to its dedicated amplifier means (FA1 . . . FA4), and (d) the pump signals are separated from the amplified wavelength channel signals obtained from the amplifier means and a second multiplexing is carried out, combining the amplified wavelength channel signals into an outgoing WDM signal.

Abstract: A technique for polarization locking optical outputs of N optical amplifiers to a reference polarization output, N being an integer, includes providing N optical loops and a reference optical loop. Each of the N optical loops includes a polarization controller connected to an optical amplifier. The reference optical loop includes a reference polarization controller and a linear optical polarizer. An optical output from a laser source is fed to all of the polarization controllers. A portion of an optical output of the reference polarization controller is fed back to an input of the reference polarization controller via the linear polarizer. A portion of the optical output of the reference polarization controller is fed to an optical input of each of N beam splitters and an optical output of each amplifier of the N loops is fed to an optical input of a respective one of the N beam splitters. A substantial portion of the optical output of each amplifier is output by its respective beam splitter.

Abstract: An optical repeater is described which integrates an erbium doped optical fiber amplifier (EDFA) with a dispersion equalizer (DE) based on fiber gratings. The dispersion equalizer is based on parallel connection of a plurality of fiber gratings, or on parallel connection of a cascaded plurality of fiber grating branches, each branch carrying a plurality of gratings coupled in series. Each grating in each branch is chirped to provide selective reflection at one of the plurality of signal carrier wavelengths so that the total optical bandwidth of the dispersion equalizer is enhanced, i.e. the total bandwidth for a specific signal carrier wavelength is the combined optical bandwidths of the gratings which provide the reflection at the wavelength. The use of multiple gratings for each wavelength improves the optical bandwidth of the equalizer compared with single grating designs, enhancing the effective bandwidth.

Abstract: A wideband optical amplifier for amplifying an input optical signal of known wavelength in one of at least two bands of wavelength has a significantly small number of optical components and thus is low cost. The wideband optical amplifier includes: a first set of a first optical coupler, a first pump light source, and a first erbium doped optical fiber (EDF) for pumping the first EDF; an optical switch for changing an output signal of the first set; and a second set of a second optical coupler, a second pump light source, and a second EDF for pumping the second EDF. In another aspect, a wideband variable wavelength optical source is achieved by utilizing the wideband optical amplifier described above.

Abstract: An ultra-wide bandwidth optical amplifier for the 1.5 &mgr;m optical band divides the 1520 nm-1610 nm bandwidth into three narrow bandwidths, i.e. C1 (1520 nm-1541 nm), C2 (1541 nm-1565 nm) and L (1565 nm-1610 nm), and uses three separate erbium doped fiber amplifier blocks, configured in parallel relation and individually optimized to separately amplify the respective bandwidth. Multipath interference is controlled by constructing all three amplifier blocks with the same optical transmission length. The C1 and C2 band amplifier blocks, which include shorter erbium doped fibers than the L band amplifier block, are physically lengthened using lengths of single mode fiber so that the total length of the optical transmission path of each amplifier block is generally equal. Fiber lengths are controlled to within 500 microns.

Abstract: A modular architecture for a unidirectional fiber amplifier provides separate optical amplification for a short and long band transmission channels of a wide-band optical signal. The modular amplifier comprises a first gain stage that amplifies the short band and passes through the second-band, and a second gain stage connected in series with the first gain stage that amplifies the long band. The short band by-passes the second stage. The length of the doped fiber and the population inversion of active fiber of the first stage are selected to give an average inversion in excess of about 50%, while the length of the doped fiber and the population inversion of active fiber of the second stage are selected to give an average inversion in excess of about 50%.

Abstract: An optical transmission system has been designed to optimize the use of the spectral emission range of rare-earth-doped fiber amplifiers. The system includes a wide band of channels in the spectral emission range of erbium-doped fiber amplifiers, which is split into two sub-bands, a low sub-band corresponding to the low end of the range and a high sub-band corresponding to the high end of the range. The two sub-bands are separately amplified and optimized, and then recombined without significant competition between the two sub-bands. In addition, an equalizing filter, such as a specialized Bragg filter or interferential filter, is applied to the low sub-band instead of the entire band of channels, thus greatly reducing any equalization need or unequalization effects.

Abstract: An optical fiber amplifier for WDM-signals comprises an active optical fiber pumped with pumping light from a pump source. In order to give the amplifier a constant gain for the WDM-signals irrespectively of the number of active WDM-signals an additional light source is arranged to inject, when required, extra light into the active optical fiber, at least in a portion thereof, through a power combiner. The injected light has a wavelength different from that of the WDM-channels and preferably longer so that it will not cause an amplifying or pumping effect in the active optical fiber but so that it still can be amplified in the active fiber. The light source is controlled by a signal derived from an output power measurement device so that it will inject extra light when a WDM-channel becomes inactive. The power of the extra light is thus selected to saturate the optical fiber amplifier at a constant gain irrespectively of the number of signal channels, i.e. of the total power of the input light signals.

Abstract: The present invention provides a method and device for to implement time division multiplexing of a fiber optic serial Bragg grating sensor array containing more than one Bragg grating. The device provides a pulse read-out system that allows for a reduction in system noise and an increase in sensor resolution and flexibility. The optical signals reflected from the Bragg grating sensors are gated by an electronically controlled optical modulator before any wavelength measurement is performed to determine the sensor information. This offers significant advantages since the sensor information is encoded into the wavelength of the optical signal and not its intensity. Therefore the sensor signal information is not distorted by the gating.

Abstract: A plurality of copper lasers, as radiant power sources, emits a beam of power carrying radiation. A plurality of fiber injection assemblies receives power from the plurality of copper lasers and injects such power into a plurality of fibers for individually transmitting the received power to a plurality of power-receiving devices. The power-transmitting fibers of the system are so arranged that power is delivered therethrough to each of the power-receiving devices such that, even if a few of the radiant power sources and/or fibers fail, the power supply to any of the power receiving devices will not completely drop to zero but will drop by the same proportionate amount.

Abstract: An apparatus and method for controlling the gain in an erbium-doped fiber amplifier (EDFA) incorporated into a multi-wavelength communication system so as to amplify each of the wavelength signals. The amplifier operates near to saturation so that, if one or more of the multi-wavelength signals is removed from the transmission, the remaining channels are increasingly amplified, leading to problems with other components in the system which depend upon intensity. According to the invention, an optical signal at a wavelength that is not within any of the transmission channels is selectively fed back around the amplifier and caused to lase in a wavelength-filtered ring-laser configuration. The lasing signal governs the saturation of the amplifier such that any gain shed by a disappearing data signal is predominately used by the lasing signal, not by the remaining data signals. Thereby, the data signals do not experience gain variations dependent upon the number of data signals being amplified.

Abstract: It is the object of the invention to provide a WDM optical transmission system, in which the transmission performance of the system is optimized by keeping an optical power per an optical signal constant, independent of the number of the optical signals. An alternating current (AC) voltage of a frequency f.sub.1 is supplied to a burst generator, and control bursts S.sub.1 to S.sub.n (frequency f.sub.1) with different transmitting times are generated by the burst generator. These control bursts are respectively supplied to laser diodes (LDs) provided with control circuits, and directly modulate the output of the LDs. Moreover, the output of the LDs are respectively modulated by external optical modulators, multiplexed by an optical coupler and emitted to an optical fiber.

Abstract: A loss-less, optical add/drop multiplexer according to the present invention includes a rare earth-doped fiber amplifier integrated with a wavelength-selective fiber path coupled between two directional optical transfer devices for selectively adding and dropping optical signals from a multi-wavelength signal, such as a wavelength division multiplexed optical signal. One or more fiber gratings are disposed along the length of the rare earth-doped fiber amplifier or between segments of the rare earth-doped fiber so that at least one grating is used for reflecting each optical signal that is expected to be added to or dropped from the multi-wavelength optical signal. By using this configuration, appropriate amplification is provided to compensate for losses in the add, drop, and through paths.

Abstract: A broadband light amplifier comprising a pair of signal transmission and amplification arms, one for carrying a short wavelength signal in a short optical wavelength band and another for carrying a longer wavelength signal in a longer optical wavelength band, an optical amplifier in each arm for amplifying a respective signal carried therein, and a wavelength division optical multiplexer for combining the amplified signals into a single optical fiber, the amplifier being devoid of a circulator.