JPS60237339A - Apparatus for evaluating optical circuit - Google Patents

Abstract

PURPOSE:To effectively perform the evaluation of an optical circuit including a light wave guide, by mounting a means for effectively connecting oscillation light to the optical circuit, a means for detecting the transmitted light of the optical circuit and a means for detecting light laterally scattered in the optical circuit. CONSTITUTION:Oscillation light 2 with a wavelength of 1.06mum from a Nd:YAG laser 1 is guided to a single mode silica fiber 4 through an optical coupling system 3 and induction Raman scattered light 5 obtained from the other end of the fiber is guided to an optical circuit 7 having a light wave guide through the other one light coupling system 6. The transmitted light 8 emitted from said optical circuit 7 is spectrally divided by a spectrometer 9 and detected by a Ge light detector 10. The scattered light 11 generated in the optical circuit 7 is divided spectrally by an interference filter 12 and detected by the other one Ge light detector 13. By synthesizing the result in each wavelength by this method, the characteristic of the light wave guide can be evaluated.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an optical circuit evaluation device having a novel configuration.

(Prior Art and its Problems) With the recent rapid progress in optical application system technology including optical communications, interest in optical circuits including passive optical waveguides is increasing. Such optical circuits include those made of glass or GaAs p InGaAsP.
etc.Φ4. -There are products using group V compound semiconductors or their mixed crystals, but all of them have a one-dimensional or two-dimensional optical confinement structure, and are used for passive purposes such as branching and coupling, or for control purposes such as switching and exchange. It is used for a purpose. As demands for performance and reliability in various systems become more sophisticated, similar demands are also becoming stronger for optical circuits.

Loss in optical circuits, especially in optical waveguides? There are various types of optical waveguides, such as mode characteristics 9 and interstitial characteristics, but recently there has been an increasing demand for optical waveguides with low loss due to the fact that problems such as mode conversion are less likely to occur in a single mode suitable for use for control purposes. ing.

Conventionally, such optical circuits have been evaluated using V-za light or incoherent light sources such as tungsten lamps, but in the former case, only a single wavelength can be measured. However, in the latter case, the drawback that coupling to an optical circuit is extremely difficult cannot be avoided. However, it is often necessary to carry out measurements by including an optical waveguide, and for this purpose, there has been a demand for a light source and measurement device that can be easily coupled to an optical waveguide and has a wide spectrum width. Conventionally existing dye lasers have not been sufficient for this purpose in terms of spectral width and handling.

(Objective of the Invention) The present invention eliminates such drawbacks in conventional optical circuit evaluation devices, makes it possible to perform various measurements and evaluations using a light source with an extremely wide spectral width, and thereby makes it possible to An object of the present invention is to provide an optical circuit evaluation device that can effectively evaluate an optical circuit including a wavepath.

(Structure of the Invention) The present invention is a stimulated Raman oscillator in which the light source has oscillation light in the wavelength range to be measured of the optical circuit, a means for effectively coupling the oscillation light to the optical circuit, and a means for effectively coupling the oscillation light to the optical circuit, and The structure includes at least means capable of directly or spectrally detecting light and means capable of directly or spectrally detecting light scattered laterally in the optical circuit.

(Operation/Principle of the Invention) As mentioned earlier, in precise evaluation of optical waveguides, it is not enough to simply look at the transmission characteristics at one wavelength, but also to examine the scattering and
It is necessary to know the optical loss caused by mode conversion etc. and its interdependence with wavelength. Conventionally, a light source with a wide spectral width generally has a small area, so it has been difficult to couple it effectively with a single mode fiber. However, recently developed stimulated Raman oscillators using silica fibers make it possible to extract light with an extremely wide spectrum width from an extremely small area. Furthermore, by measuring scattered light in addition to the conventional measurement of transmission characteristics, it becomes possible to perform a more detailed evaluation of the optical circuit.

(Example) In order to further clarify the advantages and main features of the present invention, an example will be described below.

As shown in Figure 1 of the drawings, Nd:YAG laser (Shun Z
・The oscillation light (2) with a wavelength of 1.06 μm is connected to the optical coupling system (3).
) into a single mode silica fiber (4) and the stimulated Raman scattered light (5) obtained from the other end of the fiber.
is guided to an optical circuit (power) having an optical waveguide through another optical coupling system (6).The transmitted light (8) emitted from the optical circuit
is subjected to spectroscopy by a spectrometer (9) and then detected by a Ge photodetector (l
O). On the other hand, the scattered light (11) generated in the optical circuit is separated by an interference filter (121) and detected by another Ge photodetector.

Figure 2 shows the wavelength relationship between incident light (21+ = transmitted light (2) and scattered light (c) in an optical circuit having an optical waveguide made of InGaAsP mixed crystal formed on an InP crystal substrate. Light has a nearly continuous spectrum at wavelengths longer than 1.2 μm.On the other hand, transmitted light has a distinct short-wavelength edge (2( A), and a decrease (251) corresponding to the mode cut-off appears on the long wavelength side.On the other hand, the scattered light is caused by Rayleigh scattering and Cummie scattering due to transient modes caused by imperfections in the optical waveguide wall. Although it is generally complicated as there are various types of wavelengths, it is possible to evaluate the optical waveguide characteristics by integrating the results at each wavelength.

In the embodiment shown in FIG. 1, substantially the same effect can be obtained by using means for bringing the output hole of the single mode fiber extremely close to the optical circuit under test instead of using the coupling system 6.

Furthermore, by employing an infrared vidicon and using it together with an interference filter to know the two-dimensional distribution of scattered light, it is possible to more clearly know the cause of light loss due to scattering. Furthermore, when evaluating a device having multiple boats, such as an optical branch, more effective measurements can be made by measuring the output light of each output boat or by exchanging the entry and exit of each boat.

The light source only needs to have a wide spectrum width and a small area, but currently the best one is one using stimulated Raman oscillation of a low-loss single-mode silica fiber. In addition, InGaAs, which is of great practical importance,
For measurement of optical waveguides made of P mixed crystal, Nd:Y
Adoption of an AG laser is also advantageous.

(Effects of the invention) As a result, circuit characteristics and material characteristics that were impossible when using a conventional tungsten lamp as a light source have been improved.
It has become clear that this can be done quickly and accurately. In particular, this evaluation method is suitable for evaluating devices with complex structures such as optical branching switches or devices with dynamic characteristics.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an embodiment of an optical circuit evaluation device according to the present invention. 1, Nd: YAG laser 2. 1.06 μm oscillation light 3, optical coupling system 4, single mode silica fiber 5, stimulated Raman light 6, optical coupling system 7, optical circuit including optical waveguide 8, transmitted light 9, Spectrometer 10, Oe photodetector 11, scattered light 12, interference filter 13, Oe photodetector FIG. 2 is a diagram showing the spectral distribution of each of the incident light, transmitted light, and scattered light of the optical circuit. 21, incident stimulated Raman light 22, transmitted light 23, scattered light 24, edge due to absorption edge of transmitted light

Claims (1)

[Claims] 1. A light source consisting of a stimulated Raman oscillator that emits oscillation light in the measured wavelength region of an optical circuit, means for effectively coupling the oscillation light to the optical circuit, and direct or spectroscopic detection of the transmitted light of the optical circuit. What is claimed is: 1. An optical circuit evaluation device comprising at least means capable of detecting light scattered laterally in the optical circuit, and means capable of directly or spectrally detecting light scattered laterally in the optical circuit.