| 摘要 |
PURPOSE:To obtain a highly accurate temp. sensor, by forming a light transmission path by providing a semiconductor, of which the light absorbing characteristics are changed by temp., and a reflective plate to the leading end of one optical fiber and reciprocally transmitting lights having two kinds of wavelengths to said transmission path. CONSTITUTION:The light of a short wavelength LED11 with a central wavelength lambda1 and light intensity P1 is equally divided by a half mirror 21 to be reflected by LPF71 and light with light intensity of P1/2 is received by a light receiver 31 while the other light with light intensity of P1/2 straightly transmits through a half mirror 22 to be converted to light with light intensity P1/4 which, in turn, enters into an optical fiber 4 to reach GaAs 5 and is reflected by a reflector 6 to be returned to the half-mirror 22. The light of a long wavelength LED12 with a wavelength lambda2 and light intensity P2 is equally divided by the half mirror 21 and light with intensity of P2/2 is received by a light receiver 33 while the other light with light intensity of P2/2 passes through the half mirror 22 to obtain light with light intensity of P2/4 which is, in turn, reflected by the reflector 6 in the same way to be returned to the half mirror 22. When the transmission loss of a light path is L and the light absorbing loss of an element 5 is A(T), the ratio of light intensity P1' with the wavelength lambda1 received by the light receiver 32 through LPF72 and light intensity P2' with the wavelength lambda2 received by the light receiver 33 comes to A(T). That is, the loss of the light transmission path or the variation in the light intensity of LED is removed by this constitution and a sensor utlizing only the light absorbing characteristics of GaAs 5 is obtained.
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