The full fiber type fibre optic current sensor of development need adopt extraordinary magneto-optic optical fiber and polarization to keep Transmission Fibers, cost costliness both at home and abroad at present; Packaged structured optical fiber current sensor is to avoid the disturbance of transmission optical polarization in the optical fiber to adopt multimode optical fiber, but in fact multimode optical fiber still exist can be comparable with current sensing signal the polarization state random perturbation, and multimode optical fiber is subject to the external environment influence and loss fluctuation takes place, make output light signal instability, cause the detection error.On the other hand, the Verdet constant of magneto-optic memory technique becomes with temperature, need carry out temperature compensation and proofread and correct.In existing technique for temperature compensation, as Taiwan patent of invention " temperature compensating type fiber optic current sensors " (notification number 234742, application number 83102850, polished, the Li Guocheng of inventor Li Yan), be that current sense and temperature sensing light path are separated, the sensing head structure of Gou Chenging is comparatively complicated thus, and is subject to disturb, cause thermometric inaccurate, influence the temperature compensation performance.
Shortcoming at above-mentioned prior art exists the objective of the invention is: (one) designs of the present invention optical fiber polarisation attitude control structure, both can adopt multimode optical fiber also can adopt single-mode fiber, have the function that the disturbance to the optical fiber polarisation attitude compensates automatically; (2) device of the present invention also has temperature compensation function simultaneously, and temperature sensing and current sense light path are united two into one, and the sensing head structure is greatly simplified.
Fibre optic current sensor of the present invention is made up of light source, wavelength division multiplexer, sensing head, input optical fibre, output optical fibre and photo-detector etc.Produce two kinds of wavelength X with two light sources 1 and 2
2Light beam, utilize wavelength division multiplexer 3 that the light beam coupling of two kinds of wavelength is entered and transfer to sensing head 5 in the input optical fibre 4, described sensing head is connected successively by polarizing beam splitter 6, magneto-optic element 7, temperature-sensing element 8 and analyzing coupling mechanism 9 and forms, this sensing head links by output optical fibre 10 and another wavelength division multiplexer 11, this wavelength division multiplexer with the light signal of two kinds of wavelength transmitting in the output optical fibre separately and deliver to two photo-detectors 12 and 13 is converted to electric signal by photo-detector with light signal.
Temperature compensation of the present invention is realized by following technology: in sensing head 5, the wavelength that is transmitted by input optical fibre 4 is λ
2Light signal when the temperature-sensing element 8, a kind of wavelength (λ
1) light wave intensity vary with temperature and change, constitute temperature measurement signal, and another kind of wavelength (λ
2) light wave intensity do not vary with temperature, constitute the thermometric reference signal, through output optical fibre 10 deliver to wavelength division multiplexer 11 with the light signal of two kinds of wavelength separately and after photo-detector 12 and 13 opto-electronic conversion, deliver to follow-up signal processing unit output temperature signal, the power supply flow sensor is made the usefulness of temperature compensation.
Polarization state compensation of the present invention is realized by following technology: in sensing head 5, the wavelength that is transmitted by input optical fibre 4 is λ
2The random polarization state light signal be polarized optical splitter 6 and be divided into two bundle polarization states orthogonal linearly polarized lights, their its polarization states through magneto-optic element 7 time change with current signal respectively, detect two-beam wave polarization attitude by analyzing coupling mechanism 9 afterwards, optical polarization is converted to light intensity with the variation of electric current is coupled into output optical fibre 10 with the variation of electric current and with the two-beam ripple, through wavelength division multiplexer 11 demultiplexings and after photo-detector 13 opto-electronic conversion, deliver to follow-up signal processing unit output current signal.Since the polarization state disturbance for two linearly polarized lights to influence polarity opposite, cancel out each other, make the current signal of output and light wave input polarization have nothing to do, promptly realized the control and the compensation of polarization state.
Advantage of the present invention: (one) can adopt standard transmission optical fiber, has reduced device cost; (2) designed optical fiber polarisation attitude control and collocation structure automatically, made because polarization state and loss disturbance that optical fiber causes are reduced; (3) current sense and temperature sensing light path are united two into one, the sensing head structure is greatly simplified, also can adopt the stability and reliability of dual wavelength detection technique raising temperature detection simultaneously, strengthen the effect of temperature compensation.