A remote optically pumped amplifier in a multi-span optical communications link. A backwards Raman pump module performs backwards Raman amplification in an optical communications span that contains the remote optically pumped amplifier. A residual amount of backwards Raman pump power is then used to power the remote optically pumped amplifier. The remote optically pumped amplifier may be located 40 to 120 kilometers in optical distance from the backwards Raman pump module such that at least three milliwatts of residual Raman pump power is received by the remote optically pumped amplifier. The Raman pump module may be a multi-pump Raman pump module. A controller controls pump power provided by at least one of the pumps of the backwards Raman pump module, so as to at least partially compensate for optical signal strength versus wavelength variation introduced by the remote optically pumped amplifier and the backwards Raman pump module.

A white light spectroscopy system includes a super continuum light source having an input light source including semiconductor diodes to generate an input beam having a wavelength shorter than 2.5 microns. The light source includes a cladding-pumped fiber optical amplifier to receive the input beam, and a photonic crystal fiber to receive the amplified optical beam to broaden the spectral width to 100 nm or more forming an output beam in the visible wavelength range. The output beam is pulsed with a repetition rate of 1 Megahertz or higher. The system also includes a lens and/or mirror to receive the output beam, to send the output beam to a scanning stage, and to deliver the received output beam to a sample. A detection system includes dispersive optics and narrow band filters followed by one or more detectors to permit approximately simultaneous measurement of at least two wavelengths from the sample.

A method for realizing precise gain control for a hybrid fibre amplifier, and a hybrid fibre amplifier, in which by an erbium-doped fibre amplifier firstly outputting a constant power, a comparable source signal optical power is provided for a raman fibre amplifier of a next stage. A feedback for the gain control may be formed by comparing a source signal optical power calculated after starting pumping of the Raman fibre amplifier and a source signal optical power detected after pumping stops, thereby greatly improving gain control precision of the Raman fibre amplifier. Moreover, the erbium-doped fibre amplifier parts of all the hybrid fibre amplifiers may simultaneously output a constant optical power, and the Raman amplifier parts of all the hybrid fibre amplifiers may simultaneously start calibration, so that the time for starting operation of the entire system may be improved greatly.

A downhole sensing method includes modulating light to form a soliton that propagates through an optical fiber acting as a sensing element that measures a downhole parameter. The method further includes obtaining scattered light created as the soliton propagates through the optic-fiber. The method further includes determining a value for a downhole parameter based on the scattered light, and displaying a representation of the value.

A hybrid fiber amplifier and method of adjusting gain and gain slope of thereof. The hybrid fiber amplifier comprises: RFA and EDFA that does not comprise variable optical attenuator. The RFA comprises pump signal combiner, pump laser group, out-of-band narrow-band filter, and photodetector. The EDFA comprises input coupler, erbium-doped fiber, output coupler, input photodetector, and output photodetector that are connected in sequence. The hybrid fiber amplifier also comprises control module that coordinates and controls EDFA and/or RFA to adjust gain and/or the gain slope based on desired amplification requirements. The EDFA and/or RFA can be coordinated and controlled by using the control module to achieve desired amplification effect. In addition, the EDFA does not comprise the variable optical attenuator, which avoids problems caused by the variable optical attenuator. The hybrid fiber amplifier and method of adjusting gain and gain slope thereof are applicable to technical field of optical communications.

A measurement apparatus includes sensors adapted to be coupled to tissue containing blood and configured to generate signals associated with physiological parameters. The device is configured to communicate with a software application through a base device. The software application is configured to operate on a control system. The control system is capable of receiving physiological parameter signals. The control system includes a touch-screen, a proximity sensor, circuitry for obtaining movement information from a positioning sensor, a mechanical system having actuators, and a wireless transmitter to transmit data to a host. The software application is operable to generate the physiological information based on the signals from the sensors. The control system is further configured to receive voice input signals and manually entered input signals. The host is configured to generate status information from the data and includes a memory storage device and a communication device.

A modular, compact and widely tunable laser system for the efficient generation of high peak and high average power ultrashort pulses. Peak power handling capability of fiber amplifiers is expanded by using optimized pulse shapes, as well as dispersively broadened pulses. Dispersive pulse stretching in the presence of self-phase modulation and gain results in the formation of high-power parabolic pulses. To ensure a wide tunability of the whole system, Raman-shifting of the compact sources of ultrashort pulses in conjunction with frequency-conversion in nonlinear optical crystals can be implemented, or an Anti-Stokes fiber in conjunction with fiber amplifiers and Raman-shifters are used. Positive dispersion optical amplifiers are used to improve transmission characteristics. An optical communication system utilizes a Raman amplifier fiber pumped by a train of Raman-shifted, wavelength-tunable pump pulses, to thereby amplify an optical signal which counterpropagates within the Raman amplifier fiber with respect to the pump pulses.

A cascade control system of an optical fiber amplifier includes a target setting parameter module, a primary controller, at least one controlled module and a secondary controller corresponding to the controlled module. The control system adopts two or more cascade control loops so that disturbance entering into the secondary loop can be overcome quickly, thereby the dynamic characteristics of the system may be improved. The primary controller aims to coarse adjustment and overall target control, and the secondary controller aims to fine adjustment and quick convergence of a short-term target, so that the control quality of the cascade control system may be further improved. The cascade control system may define the overall control target directly in the primary loop and avoid impact of aging characteristics of some special parameters on the application.

The present disclosure relates to a technical field of optical communication, and provides a method and an apparatus for determining maximum gain of Raman fiber amplifier. Wherein the method includes obtaining transmission performance parameters of a current optical fiber transmission line; respectively obtaining impact factors A.sub.1, A.sub.2, A.sub.4 according to a distance between a joint and a pump source, a fiber loss coefficient, and a fiber length included in the transmission performance parameters; calculating a joint loss value Att.sub.Aeff according to a distance between a joint and a pump source, a fiber loss coefficient, and looking up impact factor A.sub.3 according to Att.sub.Aeff; determining an actual maximum gain which may actually be achieved by the Raman fiber amplifier according to A.sub.1, A.sub.2, A.sub.3, A.sub.4. The actual maximum gain obtained in the present disclosure is the maximum gain that may be achieved over all input power ranges, and the original signal in system is kept to operate at a fixed gain, such that a gain locking effect is realized, and fluctuation of existing transmission signal power caused by signal change in transmission fiber link is avoided.

The embodiments of the present invention disclose a method and an apparatus for determining a gain of a Raman optical amplifier and a Raman optical amplifier. The method includes: acquiring present gain parameter information of a Raman optical amplifier; and determining a present gain of a monitoring channel of the Raman optical amplifier according to the present gain parameter information and a correspondence between a gain of the monitoring channel of the Raman optical amplifier and gain parameter information. According to the method and apparatus for determining a gain of a Raman optical amplifier and the Raman optical amplifier that are in embodiments of the present invention, a present gain of a monitoring channel can be accurately determined; therefore, a gain spectrum of the Raman optical amplifier can be accurately monitored, and the gain of the Raman optical amplifier can be accurately adjusted to a target gain.