Abstract: A gain control circuit for an optical amplifier includes a feed-forward path which enables the pump power of an excitation laser to be controlled based on input power of the amplifier. The feed-forward path is complemented by a feed-back loop which includes: a subtractor that outputs an error signal based on a difference between scaled input power and output power of the optical amplifier; a regulator which generates a bias and correction signal that reduces the error signal to zero; and an adder which adds the bias and correction signal to the input power signal of the feed-forward path. The output of the adder forms a pump control signal which maintains a desired gain of the amplifier irrespective of fluctuations in input power and channel load changes, as well as other influences. Through the use of purely electronic control, the control circuit controls the gain of the amplifier with substantially less pump power than conventional circuits utilizing other known methods.

Abstract: A pumping source for Raman amplification of an optical wavelength-division multiplex signal which has a number of pump lasers with different pumping wavelengths in each case. The pumping wavelengths are selected in such a way that mixing products from a four-wave mixing are minimized in or removed from the signal spectrum. Transmission bands for the channels of the WDM signal also can be defined in the signal spectrum such that the mixing products are situated between the transmission bands. Differences in the signal-to-noise ratios between the channels of the WDM signal on the basis of four-wave mixing are, therefore, efficiently minimized in the signal spectrum.

Abstract: Disclosed are an optical transmission system and a Raman amplifying control unit that can stabilize the effective loss of a transmission line even if the optical transmission system has a relay station between a transmitting station and a receiving station. The optical transmission system and the Raman amplifying control unit have an introducing means for outputting inspection light and introducing it to the transmission line, a receiving means for receiving the back-scatter from the inspection light, and a control means for inspecting the transmission line and controlling an exciting light supplying means according to the received backscattering light. The introducing means, the receiving means, and the control means are provided together with the exciting light supplying means in a station at the transmitting side or receiving side of a relay section in the optical transmission system.

Abstract: An optically amplified gain control circuit is disclosed, which comprises an optically amplifying medium for amplifying an optical signal, a exciting light coupler for combining exciting light with the optical signal optically amplified by the optically amplifying medium, and a control circuit for controlling an output of the exciting light combined with the optical signal by the exciting light coupler, wherein the optical signal to be amplified is composed of a main signal, an SV signal, and a tone signal which are multiplexed, and wherein the control circuit controls the output of the exciting light corresponding to the tone signal on the preceding stage of the optically amplifying medium and the tone signal on the next stage of the optically amplifying medium so as to control the amplification of the optical signal by the optically amplifying medium.

Abstract: The dynamic range of an optical amplifier is extended by the addition of a power control circuit. A switch is interposed between a current source and an optical pump supplying pumping light to the gain medium of the optical amplifier. A modulated signal such as a pulse-width modulated signal is used to actuate the switch and control a relative duration of the “on” and “off” periods of the electrical current supplied to the optical pump. Gain latency in the optical amplifier permits a substantially continuous signal to be output from the optical amplifier in response to the switched electrical current supply to the optical pump. A controller may used a feedback signal from the optical pump or from a power monitoring device to control the modulator and, thereby, the switch. A target pump power level, target gain or target amplified signal power level may also be applied in a feedback control loop that controls the modulator and switch.

Abstract: We report an optical pulse-compression technique based on quadratic nonlinear media. Negative nonlinear phase shifts are generated via phase-mismatched second-harmonic generation, and the phase-modulated pulses are then compressed by propagation through materials with normal dispersion. Millijoule-energy pulses from a Ti:sapphire amplifier are compressed from 120 to 30 fs, and calculations indicate that compression ratios>10 are realistically achievable using this approach with optimal materials. The insertion loss of the compressor can be less than 10% of the pulse energy, and scaling to higher pulse energies will be straightforward.

Abstract: An optical amplifier for amplifying the channel signals of a WDM signal comprises an amplifier arrangement for amplifying a band of the channels. The amplifier arrangement comprises an amplifier (6) and a filter (8). The filter comprises a controllable optical filter having an attenuation characteristic which comprises a region of positive gradient and a region of negative gradient with respect to input frequency. The magnitude and alignment along the frequency axis of the attenuation characteristic is variable, such that the filter can be tuned to provide gain flattening for the amplified band of channels. The filter can be tuned to the requirements of a particular sub-band, whilst identical filters can be used for each sub-band. This invention enables identical filters to be used, and gives good pump power efficiency, as the attenuation of each filter can be controlled to the desired level, thereby avoiding the need for large increases in pump power.

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: 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 amplifier. The amplifier includes a plurality of pump radiation sources, each pump radiation source adapted to produce radiation having a set of pump wavelengths and pump powers corresponding to the respective pump wavelengths, wherein at least one set is different from at least one other set. The amplifier also includes a plurality of pump radiation combiners and a coupler. The coupler is optically coupled to the outputs of the pump radiation combiners, receives the coupled radiation from the pump radiation combiners and outputs pump radiation profiles to respective coupler outputs. The amplifier also includes pump-signal combiners, each optically coupled to a respective coupler output of the coupler outputs, which are adapted to couple an optical signal with the respective pump radiation profiles.

Abstract: The present invention relates to an optical amplifier comprising a structure which prevents transmission quality from lowering and enables constant gain control with a higher speed and higher accuracy. In a typical embodiment of the present invention, amplified light from an EDF is once guided to an optical filter by way of an optical circulator. Of thus guided amplified light, noise light passes through the optical filter, whereas each of signal components is reflected thereby, so as to separate the noise light and signal components from each other. The noise light having passed through the optical filter is detected by a photodetector, and gain control is carried out by a gain control circuit so as to suppress fluctuations in the detected noise light power.

Abstract: The present invention relates to an optical amplifier system in which multiple laser cavities are utilized to control the gain of an erbium doped fiber amplifier (EDFA). More specifically, the present invention is directed to an optical amplifier comprising a gain medium such as an erbium doped optical fiber which provides gain for an optical signal propagating therein. The gain medium also provides gain for a plurality of laser cavities (e.g. first and second laser cavities) which simultaneously oscillate at individual (e.g. first and second) wavelengths. The inventive optical amplifier results in reduced variation in gain spectrum as a function of input signal power, as a function of wavelength, and as a function of time. By varying the optical attenuation in one or more of the individual laser cavities it is possible to vary the gain spectrum of the gain medium at the corresponding individual wavelength and this controls the shape of the gain spectrum of the gain medium.

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: A semiconductor optical amplifier system comprises a hermetic package. In the typical implementation, this hermetic package is a standard 0.75 inch×0.5 inch package, such as a butterfly package. An optical bench is sealed within this package. A first fiber pigtail enters this package via a feed-through to connect to the bench and terminate above the bench. A second optical fiber pigtail enters the package via a second fiber feed-through to connect to the bench and similarly, terminate above the bench. A semiconductor amplifier chip is connected to the bench to provide amplification. Isolators are further incorporated along with a monitoring diode to yield a fully integrated system.

Abstract: An optical amplifier apparatus is provided with an optical amplifier and a 4-port optical circulator. The optical amplifier optically amplifies first signal light entered from an input port thereof, and then outputs the first amplified signal light from an output port thereof. The optical circulator contains first to fourth ports, and sequentially outputs light that is inputted from each of these first to fourth ports to the next port thereof. The input port of the optical amplifier is connected to the second port, and the output port thereof is connected to the third port. An optical transmission apparatus having a break point detecting function is provided with an optical time domain reflectometer for outputting an optical pulse along the same direction as that of the first signal light in addition to the optical amplifier apparatus and an optical transmitter module.

Abstract: A multi-stage optical amplifier includes an optical fiber with at least a first Raman amplifier fiber and a second Raman amplifier fiber. The optical fiber is configured to be coupled to at least one signal source that produces at least a signal wavelength &lgr;s and at least two pump sources that collectively produce a pump beam of wavelength &lgr;p. Pump wavelength &lgr;p is less than signal wavelength &lgr;s. Signal input, signal output and a first pump input port are each coupled to the optical fiber. The first Raman amplifier fiber is positioned between the signal input port and the pump input port. The second Raman amplifier fiber is positioned between the pump input port and signal output port. A second pump input port is coupled to the optical fiber and positioned between the second Raman amplifier fiber and the signal output port. A first lossy member is positioned between the pump input port and the signal output port.

Abstract: The present invention provides an optical function device which is capable of inverting and amplifying an optical signal of the optical communication wavelength band, and executing operation of an image optical signal, and is operable in a wide temperature range, said optical function device composed of a light transmitting medium containing a rare earth element, comprising a portion thereof doped with 1×1023 per 1 m3 or more of the rare earth element for inverting an optical signal and a portion thereof doped with 1×1021 per 1 m3 or more of the rare earth element for amplifying the optical signal with an excitation light superposed thereto.

Abstract: An optical network and an optical amplifier system provide flattened gain, constant per channel output power, and compensation for variable span losses. The optical amplifier system is disposed in a transmission line of the optical network. The optical amplifier includes a first and second stage optical feedback loop amplifiers.

Abstract: An optical isolator module in which an optical splitter for splitting an optical signal input through an input port, an optical detector for detecting the separated light, and a compensator for compensating for polarization mode dispersion are integrated into a single component along with an isolator, and an optical amplifier employing the optical isolator module are disclosed. In the optical isolator module, a first lens focuses the incident optical signal. A first birefringent device has a tapered shape in which a first incident surface forms a first predetermined angle with a first emitting surface from which a polarized light is emitted, and the incident surface of the first birefringent device is coated for partial reflection so that the portion of the incident optical signal is reflected as an reflected light. A Faraday rotator rotates polarized light by a second predetermined angle.

Abstract: A method (100) and process (120) for extending the optical bandwidth of an optical signal splitter/amplifier (160) that includes optical amplifier material and an multi-mode interference splitter. A wider bandwidth is obtained by equalizing both the gain and noise figures for the splitter/amplifier (160) as a function of the perfect focus wavelength of the splitter and the amplified spontaneous emission spectra of the gain material. The peak wavelength of the semiconductor optical amplifier material is offset a distance from the perfect focus wavelength so that the net gain of the splitter/amplifier (160) is the semiconductor gain multiplied by the insertion loss of the splitter.