A system for interrogating sensors in a fiber optical sensor network includes groups of sensors. The sensors in one group operate at different wavelengths, and the sensors of other groups may have overlapping wavelengths. A light source generates a broadband light signal, input and output means for guides the broadband light to the fiber optical sensor network for illuminating the sensors and for coupling the light signal coming from the sensors of the fiber optical sensor network to the detection system, and a detection system detects the received light signal, during a detection integration time. The system is arranged for selecting pre-dominantly the received light coming from the different sensors of a selected group of sensors using a code-division multiplexing technique and simultaneously detecting sensors of the selected group of sensors using a wavelength-division multiplexing technique.

A multi-channel sensing system is disclosed. The multi-channel sensing system includes a multi-channel sensor connector that wavelength-divides an optical pulse output from a pulsed laser into a plurality of channels in a spectrum domain, transmits each of a plurality of optical sub-pulses generated from the wavelength division to a channel path allocated for each channel in multi-channel paths, multiplexes the plurality of optical sub-pulses passed through the multi-channel paths and outputs an optical signal including the multiplexed optical sub-pulses; and a multi-channel optical phase detector that receives the optical signal output from the multi-channel connector and a reference signal which is synchronized to the pulse laser, and detects a channel-specific electrical signal that corresponds to a timing error between each of the plurality of optical sub-pulses included in the optical signal and the reference signal. At lease one of sensors is connected to at least one of the multi-channel paths.

Methods and apparatus for fast sweeping a spectral bandwidth in order to distinguish among signals received from effectively wavelength division multiplexed (WDMed) and time division multiplexed (TDMed) optical components on a single fiber. For some embodiments, a method for interrogating optical elements having characteristic wavelengths spanning a sweep range is provided. The method generally includes introducing a pulse of light, by an optical source, into an optical waveguide to interrogate at least a first set of optical elements having different characteristic wavelengths by performing a sweep of wavelengths over a period of the pulse, wherein the period is less than a round-trip time for light reflected from an optical element closest to the optical source to reach a receiver and processing the reflected light to determine a parameter based on the times at which signals are received.

An optical monitoring system comprising first and second sensor arrays interrogated via first and second optical connections from an interrogator location. The system is configured such that no wavelength is carried bi-directionally in the first and second optical connections. In typical systems the optical connections comprise trunk cables from the sensor arrays to the interrogator location.

A method is provided for determining temperature changes of an optical fibre having Fiber Bragg Grating (FBG) patterns provided in at least one portion (Portion 1) of the optical fibre. The optical fibre is connected between a first detector arrangement and a second detector arrangement. Light is emitted into the optical fibre in a first direction from the first detector arrangement, which receives reflections from the FBG patterns of the emitted light. The reflections are processed for determining a current temperature change related to the optical fibre. On the basis of predetermined criteria, light is emitted into the optical fibre in an opposite second, direction from the second detector arrangement. The second detector arrangement receives reflections from the FBG patterns of the light emitted in the second direction and the reflections are processed for determining a current temperature change related to the optical fibre.

The present application discloses a fiber distributed acoustic sensing system, including a forward pump source, a wavelength division multiplexer, an active phase-shifted grating array, a backward pump source, and a data demodulation and processing device. The active phase-shifted grating array includes several active phase-shifted gratings engraved on a same fiber, each active phase-shifted grating having a same excitation light wavelength. The active phase-shifted grating array is configured to receive a forward pump pulse and a backward pump light pulse incident from the backward pump source, so that a forward excitation light and a backward excitation light are generated in each active phase-shifted grating, and two adjacent active phase-shifted gratings are enabled to generate excitation light self interference within a same pulse duration. The data demodulation and processing device is configured to perform interference detection on a fiber phase between two adjacent active phase-shifted gratings to detect an acoustic signal acted on the fiber. According to the system in the present application, the passive reflected light interference is replaced with active excitation light interference, thus the excitation light signal has great strength and high stability, and environmental adaptability is high.

A multiple sensor fiber optic sensing system includes an optical fiber having at least first fiber optic sensors and second fiber optic sensors deployed along its length. In response to an interrogating pulse, the first fiber optic sensors generate responses in a first optical spectrum window, and the second fiber optic sensors generate responses in a second, different optical spectrum window. The responses in the first optical spectrum window are measured in a first optical spectrum channel, and the responses in the second optical spectrum window are measure in a second, different optical spectrum channel and provide simultaneous indications of one or more parameters, such as temperature and pressure, in the environment in which the sensors are deployed.

A system for interrogating sensors in a fiber optical sensor network includes groups of sensors. The sensors in one group operate at different wavelengths, and the sensors of other groups may have overlapping wavelengths. A light source generates a broadband light signal, input and output means for guides the broadband light to the fiber optical sensor network for illuminating the sensors and for coupling the light signal coming from the sensors of the fiber optical sensor network to the detection system, and a detection system detects the received light signal, during a detection integration time. The system is arranged for selecting pre-dominantly the received light coming from the different sensors of a selected group of sensors using a code-division multiplexing technique and simultaneously detecting sensors of the selected group of sensors wavelength-division multiplexing technique.

The invention relates to a method for determining temperature changes of an optical fibre (250) having Fiber Bragg Grating (FBG) patterns provided in at least one portion (Portion 1) of said optical fibre (250), said optical fibre (250) being connected between a first detector arrangement (210) and a second detector arrangement (220), the method comprising the steps of: emitting (s410) light into said optical fibre (250) in a first direction (D1) from said first detector arrangement (210), receiving reflections from said (FBG) patterns of such emitted light by said first detector arrangement (210), and processing said reflections for determining a current temperature change related to said optical fibre (250); on the basis of predetermined criteria, emitting (s440) light into said optical fibre (250) in an opposite, second, direction (D2) from said second detector arrangement (220), receiving reflections from said (FBG) patterns of such emitted light by said second detector arrangement (220), and processing said reflections for determining a current temperature change related to said optical fibre (250). The invention relates also to a computer program product comprising program code (P) for a computer (233; 243; 253; 500) for implementing a method according to the invention. The invention relates also to a system (289) for determining temperature changes of an optical fibre (250). The invention also relates to a platform (100) being equipped with the system (289).

The present application provides a continuous spatial synchronization monitoring device for an ocean temperature and pressure. Broadband light output by a broadband light source is converted into broadband pulsed light by using a pulse controller; then, the broadband pulsed light is demodulated by using a phase shifted fiber bragg grating unit to obtain pulsed light having multiple different wave-lengths; the pulsed light is incident to a sensing optical fiber in seawater by means of a wavelength division multiplexer; according to a Rayleigh scattering principle, backward Rayleigh scattering light returns to a control demodulation module by means of the wavelength division multiplexer; the control demodulation module performs demodulation on the backward Rayleigh scattering light, analyzes a dynamic pressure according to a phase change of a light signal, and analyzes a seawater temperature according to a wavelength change, thereby simultaneously monitoring both the pressure and temperature.