Acoustooptic switch

[Detailed Description of the Invention]

[Industrial Application] The present invention relates to a sound optical switch suitable for a lightwave pulse examination machine etc. [Description of the Prior Art] Progress of fiber-optic-communications art has a remarkable thing, and practical use is presented with many fiber-optic-communications systems. In order to maintain the transmission quality of these fiber-optic communications, various measuring instruments are used, but especially the lightwave pulse examination machine that measures obstacle point search, an optical loss per unit length, connection punctiform voice, etc. which orientation the point of rupture of an optical cable, a discontinuous point, etc. is a weight measuring instrument. The lightwave pulse which emitted this kind of lightwave pulse examination machine from the semiconductor laser driven with the pulse generator, It is made to enter into an optical fiber under test via a sound optical switch, and the method which enters a detector via a sound optical switch again, and exchanges for an electric pulse the backscattered light which arose within the optical fiber, or the Fresnel reflection light which arose in the optical fiber end is used. Generally, as for these measurement with the above-mentioned lightwave pulse examination machine, since the loss per unit length of an optical fiber changes with wavelengths of the light to spread, it is desirable to be carried out by the light of the same wavelength as the time of an optical fiber having a circuit used. For this reason, the possible sound optical switch of combination operation is especially developed to the useful wavelength of 1.3 micrometers and two waves of 1.55-micrometer lights on optical communications. As the former and this kind of sound optical switch, They are P b M o O4 and A as shown in Drawing 2. S Combine 1st single mode fiber 11 by the side of the examination machine which counters on both sides of acoustooptical devices 51, such as 2 S e s, and 2nd single mode fiber 21 of a measuring side by the collimated beam system of the 1st and 2nd lenses 45 and 46, respectively, Drive circuit 101 which has a crystal oscillator which has two different oscillating frequency for acoustooptical device 51, By changing the crystal oscillator of drive circuit 101 and driving according to the wavelength of light, the outgoing radiation light of 2nd single mode fiber 2I was made to diffract, and it had become the composition which changes and measures Optical path on 3rd converged type multi-mode fiber 31 via the 3rd lens 47. (Showa 62 and two 70th anniversary synthesis national conference public performance collected-papers work of year March 15 issue of the Institute of Electronics, Information and Communication Engineers foundation 4.P99) [Problem(s) to be Solved by the Invention] However, since the boat linked to a semiconductor laser is only single mode fiber 11 when the sound optical switch mentioned above is built into a lightwave pulse examination machine, In order to send out alternatively the lightwave pulse of a different wavelength via a sound optical switch to an optical fiber under test, Two semiconductor lasers which have a different oscillation wavelength are once connected to a separate multiplexing machine or a unification machine, After drawing the light of each wavelength in one fiber, it is necessary to connect with a sound optical switch, and an optical system becomes intricately and expensive and there is a fault that the optical loss from a semiconductor laser to an optical fiber under test becomes large. [Means for solving problem] A sound optical switch of the present invention is provided with the following. The 1st and the 2nd single mode fiber which are countered and arranged, The 1st and 2nd lenses for combining optically the 1st and 2nd single mode fibers, An acoustooptical device provided on an optic axis between the 1st and 2nd lenses, The 3rd lens and 3rd fiber that receive the optical beam which was emitted from the 2nd fiber and deflected within the above-mentioned acoustooptical device, The 4th single mode fiber and 4th lens for entering light of a different wavelength from light emitted from the 1st fiber, A prism which has an interference filter film for multiplexing and leading light which enters from the 1st and 4th fibers by reflecting light which light which enters from the 1st fiber penetrates and enters from the 4th fiber to the 2nd fiber. Therefore, since connection of the two semiconductor lasers in which oscillation wavelengths differ is directly made at the 1st and 4th fibers, respectively when the sound optical switch by the present invention is used for a lightwave pulse examination machine, an optical system becomes simple. [Example] Hereinafter, the example of the present invention is described in detail using a drawing. Drawing 1 is a sectional view showing one example of the sound optical switch by the present invention. In the figure, 1st single mode fiber 10 and 2nd single mode fiber 20 are optically combined efficiently with convergence rod lens 42 which is convergence Oy Drains 41 and the 2nd lens which are the 1st lens. On the optic axis between convergence rod lenses 41 and 42, acoustooptical device 50 which used A S 2 S e t is provided. 2nd single mode fiber 20 Exit, Optical path is changed by prism 70 and the light diffracted by acoustooptical device 50 enters into converged type fiber 30 which is the 3rd optical fiber via convergence rod lens 43 which is the 3rd lens. 4th single mode fiber 60 is arranged in parallel with 1st single mode fiber 10, and the outgoing radiation beam is collimated with convergence rod lens 44 which is the 4th lens. Prism 80 penetrates light with a wavelength of 1.3 micrometers, and pastes together the triangle prism and parallelogram prism which provided the interference filter film which reflects 1.55-micrometer light in the slope. Drive circuit 100 which drives acoustooptical device 50 has oscillating frequency 140MH7 and a 117-MHz crystal oscillator. A high frequency output with each frequency can be alternatively supplied to acoustooptical device 50 via impedance match circuit 90. At this time, light with a wavelength of 1.3 micrometers emitted from single mode fiber 10 penetrates prism 80, and combines it with single mode fiber 20, and it reflects within prism 80 and combines with single mode fiber 20 light with a wavelength of 1.55 micrometers emitted from single mode fiber 60. The wavelength of 1.3 micrometers and the 1.55-micrometer light which enter from a single mode fiber choose the output frequency of drive circuit 100 as 140 MHz and 117.4 MHz, respectively. It diffracts on the same Bragg diffraction conditions within acoustooptical device 50, and is led to converged type fiber 30 via prism 70. [Effect of the Invention] When connecting two light sources and sound optical switches which differ in an oscillation wavelength since the sound optical switch of the present invention can enter lights of two different wavelengths in a respectively individual fiber as explained above, it is effective in the multiplexing machine etc. which were formerly necessity becoming unnecessary. Therefore, with the lightwave pulse examination machine using the sound optical switch by the present invention, while an optical system can be simplified, it also has the advantage that the loss from a light source to a sound optical switch can be reduced.

[Brief Description of the Drawings]

The top view and Drawing 2 in which Drawing 1 shows the outline of one example of the sound optical switch of the present invention are a top view showing the outline of the conventional sound optical switch. 10.20.60 ...... A single mode fiber, 30.31 ...... A converged type fiber, 41, 42*43.44, 45, 46.47 ...... [ ...... An impedance match circuit, 100,101 / ...... Drive circuit ] A convergence rod lens, 50.51 ...... An acoustooptical device, 70*71.80 ...... A prism, 90.91 One congratulation Representative Patent attorney Susumu Uchihara