【正文】 transition for the light signal can be measured by the device. The transmitter, light sensitive ponents (optical fiber or the optical fiber), light receptors, signal processing system and the optical fiber by light a transmitter the light source of the optical fiber guide to sensitive ponents. At this time, the light of a certain property is measured by the regulation, already light receiving the coupling to light receptors, make the light signal into electrical signals, and finally get the signal processing to be measured. Visible, optical fiber sensor and to call for the traditional sensor based pared in measuring principle, have fundamentally different. Traditional sensor in machine, electricity measurement for the foundation, and the optical fiber sensor is based on optical measurement. Light is an electromagic wave, the far infrared wavelengths from extremely the 1mm to a far ultraviolet10nm. Its physical function and biological chemistry because one of the main electric field and cause. Therefore, to discuss the light sensitive measurement must be consider light of electricity vector of the vibration of the E, namely: Athe amplitude of the vector field E。 ωthe vibration frequency。φPhilight phase。 Tlight transmission time. Visible, if make light intensity, polarization direction of A(vector), frequency and phase one of the parameters such as with the change of state is measured and change, or is measured by A, then, through the light intensity modulation, polarization modulation frequency modulation, or phase modulation of demodulation, gain needed be measured information. Fiber optic sensors are often loosely grouped into two basic classes referred to as extrinsic or hybrid fiber optic sensors, and intrinsic or all fiber sensors. Figure 1 illustrates the case of an extrinsic or hybrid fiber optic sensor. Figure1. Extrinsic fiber optic sensors consist of optical fibers that lead up to and out of a black box that modulates the light beam passing through it in response to an environmental effect. The classification of the optical fiber sensor The classification of fiber optic sensor has some forms, can according to optical fiber sensor in the role of classification, also can according to light modulation of the tested object by the form of classification to the function of optical fiber sensor in classification Optical fiber sensor into functional, the functional and picked up three types of light type 1).Functional (all fiber type) optical fiber sensor Use has sensitive to outside information ability and the ability of testing (or special optical fiber optical fiber sensor), will pass and feeling integrated sensor. Not only the light on optical fiber effect, and still use of optical fiber in the external factors (bending, phase transformation) function, its optical properties (light intensity, phase, the change of polarization, etc.) to realize pass and sense function. Therefore, the optical fiber sensor is continuous. Due to the continuous fiber, increase its length, can improve the sensitivity. 2).The functional (or says lighttransmission type) optical fiber sensor The only light guide fiber role, the not only sense to outside information, feel function depend on other physical properties of functional ponent finish. Optical fiber discontinuous. This kind of optical fiber sensor to need not special optical fiber and other special technology, much easier to achieve, and the cost is low. But sensitivity is low, the sensitivity requirement is not too high for the occasion. 3).Pick up the light fiberoptic sensor With optical fiber probe, as received from tested object radiation light or be its reflection, scattering of light. Its typical examples such as optical fiber laser doppler velocity gauge, FuSheShi optical fiber temperature sensors, etc. to the form of light modulated by the object being measured 1).Intensity modulation fiberoptic sensors It is a use of tested object of the change sensitive ponents the refractive Signal processing Light accept the signal Light transmitter Optical fiber sensing elements index, absorb or reflection of the parameters such as changes, and lead to the light intensity changes to achieve sensitive sensors measuring. Use of optical fiber bending loss of micro。 The material of the absorption characteristics。 Vibration film or LCD reflected light intensity change。 Material because of all sorts of particle rays or chemical, mechanical incentive and shine phenomenon。 And the material of the fluorescent light radiation or the road block to form such as pressure, vibration, temperature, displacement, gas, etc. Advantages: simple structure and easy to implement, and the cost is low. Faults: light intensity by fluctuations and connectors loss of changes greatly. 2).Polarization modulation fiberoptic sensors It is a kind of polarization of light changes to deliver the tested object information of the sensor. Favorable light in magic field in the medium of the spread of Faraday effect of current, magic field sensors made。 Use light in the electric field spread a piezoelectric crystal of the bubble39。s effect of the electric field, make voltage sensor。 The light of the use of matter the effect of pressure, vibration or a sound sensors。 And the use of optical fiber birefringence sex constitute the temperature, pressure, vibration for the sensor. This kind of sensor can avoid light source of strength changes of ah, so high sensitivity. 3).Frequency modulation fiberoptic sensors It is a use of monochromatic shot to the object to be tested the reflected light changes the frequency of the monitor to the sensor. Use of sports objects reflect light and scattering light doppler effect of the optical fiber speed, vibration, pressure, flow velocity and