JPH0894494A - Optical isolator Wavelength dependence measuring device - Google Patents

Abstract

PURPOSE: To obtain an apparatus for measuring the wavelength dependency of an optical isolator accurately in a short time. CONSTITUTION: Light emitted from a white color light source 1 passes through an optical 2 and enters into a Glan-Thompson prism 3 to produce a single polarized light which is then collimated through a lens 4 and enters into an optical isolator 5a. The light leaving the optical isolator 5a is condensed through a lens 6 and enters into an optical fiber 7. Finally, it is analyzed by means of an optical spectrum analyzer 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavelength dependence measuring device for an optical isolator.

[0002]

2. Description of the Related Art When a visible light semiconductor laser is used as a light source for an optical signal transmission system for optical measurement or the like, a part of light emitted from the semiconductor laser is reflected by a transmission line or each connection portion of transmission optical parts. If the semiconductor laser is returned to the semiconductor laser, it may cause instability of oscillation characteristics of the semiconductor laser and increase noise. An optical isolator is generally used to prevent the returning light from returning.

The optical isolator basically has a magneto-optical element 13 having a Faraday effect, as shown in FIG.
It is composed of a polarizer 11, an analyzer 12, and a magnet 14 for applying a magnetic field to the magneto-optical element 13, and the magneto-optical element 13, the polarizer 11, and the analyzer 12 have their optical axes adjusted. Then, the incident light propagating in the direction of the arrow a is
After passing through the polarizer 11, it becomes linearly polarized light, enters the magneto-optical element 13, and while propagating through the magneto-optical element 13, the light is
Due to the magnetic field strength of the magnet 14, the plane of polarization normally enters the analyzer in a state of being rotated by 45 °, and the inclination of the polarizer 11 is set in advance to be equal to the inclination (45 °) of the plane of polarization of the incident light. Therefore, this incident light is transmitted. On the other hand, as indicated by an arrow b, the incident light propagating in the opposite direction has a polarization plane inclined by 90 ° with respect to the polarization plane of the polarizer 11 by passing through the analyzer 12 and the magneto-optical element 13. The incident light in the opposite direction does not pass through the polarizer 11 because it becomes linearly polarized light and enters the polarizer 11.

Wavelength dependence is one of the values indicating the characteristics of the optical isolator. This is because when the incident LD light deviates from the manufacturing center wavelength of the isolator, the Faraday rotation angle changes, and optimal isolation cannot be obtained. Therefore, the isolator as shown in FIG. 5 exhibits wavelength dependency of isolation with respect to the center wavelength.

[0005]

In order to evaluate the wavelength dependence of the optical isolator, an engineering system as shown in FIG. 6 is used. The incident light emitted from the LD passes through the Glan-Thompson prism 3 and is collimated by the collimator lens 4,
The light is condensed on the power meter 10 by the condenser lens 6.

At this time, the wavelength of the LD is gradually changed and the reverse insertion loss is measured. However,
The wavelength tunable light source 9 of the LD can change only the central wavelength of about ± 20 nm and cannot take a wide wavelength dependency. or,
In order to measure the wavelength dependence of the optical isolators corresponding to various center wavelengths, as many wavelength tunable light sources as the number of center wavelengths are required, the characteristic measuring time is long, and the equipment cost is expensive.

The object of the present invention is to eliminate the above-mentioned drawbacks,
An object of the present invention is to provide an optical isolator wavelength dependency measuring device that accurately measures wavelength dependency in a short time.

[0008]

According to the present invention, in an optical isolator wavelength dependency measuring device for measuring the wavelength dependency of isolation of an optical isolator, white light is used as a light source and isolation is performed by an optical spectrum analyzer. An optical isolator wavelength dependence measuring device characterized by being measured is obtained.

[0009]

The white light source emits light over a wide range from visible light to infrared. An isolator is placed in the forward direction with respect to the traveling direction of this light, and the wavelength dependence is measured by an optical spectrum analyzer. Next, when the optical isolator is placed in the direction opposite to the traveling direction of light, the wavelength dependence with the center wavelength of the isolator as the valley is measured. The difference between when the optical isolator is placed in the forward direction and when it is placed in the reverse direction is the wavelength dependence of the optical isolation. 4 white light sources
Since it emits light in the wavelength band of 00 nm to 1600 nm,
All optical isolators having a center wavelength in this range can be easily measured for wavelength dependence by the device according to the present invention.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail with reference to the drawings.

The structure of the present invention is shown in FIGS. Figure 1
As shown in (a), the light emitted from the end of the optical fiber 2 connected to the white light source 1 passes through the Glan-Thompson prism 3, becomes a single-polarized light, is collimated by the lens 4, and is transmitted to the optical isolator 5a. Incident. Optical isolator 5
The light emitted from a is focused on the optical fiber 7 by the lens 6.

When this light is analyzed by the optical spectrum analyzer 8, a graph as shown in FIG. 1 (b) is obtained.

When the isolator is placed in the opposite direction in the same device, the light emitted from the end of the optical fiber 2 connected to the white light source 1 passes through the Glan-Thompson prism 3 as shown in FIG. 2 (a). , Becomes a single polarized light, is collimated by the lens 4, and enters the optical isolator 5b placed in the opposite direction. The light emitted from the optical isolator 5b is condensed on the optical fiber 7 by the lens 6.

When this light is analyzed by the optical spectrum analyzer 8, a graph as shown in FIG. 2B is obtained.

The optical spectrum analyzer 8 shown in FIG.
-When the graph of FIG. 2B is displayed, the wavelength dependence of isolation is as shown in FIG.

[0016]

Comparative Example A comparative example is shown in FIG. Although the basic structure is the same as that of the embodiment, the light source is a variable wavelength light source, and the light emitted from the isolator is focused on the power meter. Therefore, the wavelength dependence is intermittently changed within the range of measurement. Variable wavelength light source is 1550nm, 1310nm
Since there are few types, the wavelength dependence can be measured only at a certain specific wavelength.

Table 1 shows the measurable wavelength range and measurement time of this example and the comparative example.

[0018]

[Table 1]

As is clear from Table 1, this embodiment has a wide measuring range and the measuring time is shortened to 1/30.

[0020]

With the device according to the invention, 400 to 16
The wavelength dependence can be easily and accurately measured in any isolator having any wavelength band up to 00 nm.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of an optical isolator wavelength dependence measuring device of the present invention. FIG. 1A is an explanatory diagram showing a configuration of an optical isolator wavelength dependence measuring device when the optical isolator is placed in the arrow direction. FIG. 1B is a graph analyzed by the optical spectrum analyzer of FIG.

FIG. 2 is an explanatory diagram showing a configuration of an optical isolator wavelength dependence measuring device of the present invention. FIG. 2A is an explanatory diagram showing the configuration of the optical isolator wavelength dependence measuring device when the optical isolator is placed in the opposite direction to that of FIG. 1A. FIG. 2B is a graph analyzed by the optical spectrum analyzer of FIG.

FIG. 3 shows an optical spectrum analyzer in FIG. 1 (b) and FIG.
The figure which shows the wavelength dependence of the isolation obtained by analyzing the graph with (b).

FIG. 4 is an explanatory diagram showing a basic configuration of an optical isolator.

FIG. 5 is a diagram showing wavelength dependency of isolation of a conventional optical isolator.

FIG. 6 is an explanatory diagram showing a configuration of a conventional device for evaluating the wavelength dependence of isolation of an optical isolator.

[Explanation of symbols]

 1 White Light Source 2, 7 Optical Fiber 3 Glan-Thompson Prism (GTP) 4 (Collimating) Lens 5a, 5b Isolator 6 (Condensing) Lens 8 Optical Spectrum Analyzer 9 Wavelength Variable Light Source 10 Power Meter 11 Polarizer 12 Analyzer 13 Magneto-Optical Element 14 Magnet a, b Arrow

Claims (1)

[Claims] 1. An optical isolator wavelength dependence measuring apparatus for measuring wavelength dependence of isolation of an optical isolator, characterized in that white light is used as a light source and the isolation is measured by an optical spectrum analyzer. Dependency measuring device.