JPH08286076A - Broadband optical fiber collimator - Google Patents

Abstract

(57) [Summary] [Purpose] A wide-band optical fiber collimator that has a small coupling loss in a wide wavelength range and can maintain its performance in a wide wavelength range when an optical system component is formed, and an optical system component using the same. I will provide a. [Structure] The broadband optical fiber collimators 8 and 18 are composed of single mode optical fibers 1 and 11 of a specific wavelength and a lens 4 respectively.
14 are coupled optical fiber collimators 8 and 18, and the coupling loss when the same optical fiber collimators 8 and 18 are faced to each other is the smallest on the shorter wavelength side than the specific wavelength. The optical system component 10 is an optical system component 10 in which the optical component 6 is arranged while facing the same optical fiber collimator 8.18 in which a single mode optical fiber 1/11 of a specific wavelength and a lens 4/14 are coupled. Thus, the coupling loss when the same optical fiber collimators 8 and 18 are faced to each other is minimum on the shorter wavelength side than the specific wavelength.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a broadband optical fiber collimator used as one component of an optical communication system or the like and an optical system component using the same.

[0002]

2. Description of the Related Art An optical fiber collimator is used as an optical component for collecting collimated light by condensing light emitted from an optical fiber and diffused by a lens. The optical fiber collimator is made by coupling a lens to an optical fiber. In the field of optical communication, two optical fiber collimators are faced to each other, and an optical component serving as a functional section is inserted between them to be used as an optical system component. It

Examples of the optical components include an optical isolator that blocks reflected return light, an optical filter that passes only light of a specific wavelength, and an optical sensor. A polarization independent optical isolator, which is an optical system component using an optical isolator as an optical component, is used as one component of an optical amplifier using an active element-doped fiber. Optical amplifiers are required to maintain their performance in the widest possible wavelength range,
Polarization-independent optical isolators also need to maintain their characteristics over a wide wavelength range.

Lenses used in optical fiber collimators include spherical lenses, aspherical lenses and gradient index lenses. Among them, spherical lenses are low in cost and their characteristics can be easily manipulated by changing their radius and refractive index. It is often used because the tilt with respect to the optical axis does not matter.

However, each lens described above has chromatic aberration. That is, the focal length of the lens is n · r /
2 (n-1) {where n is the refractive index of the lens and r is the radius of the lens}, and the refractive index of the lens has wavelength dependence. For this reason, when manufacturing an optical fiber collimator, if the lens position for the optical fiber is adjusted according to a specific wavelength, the focal points will shift at wavelengths before and after that specific wavelength, and two optical fiber collimators will face each other. Will result in a large coupling loss.

[0006]

For these reasons, it is difficult for a polarization-independent optical isolator in which an optical isolator is inserted between facing optical fiber collimators to maintain its performance in a wide wavelength range. . The same was true when an optical filter or optical sensor was used as an optical component.

The present invention has been made to solve the above problems, and has a wide band optical fiber which has a small coupling loss in a wide wavelength range and can maintain its performance in a wide wavelength range when an optical system component is formed. An object of the present invention is to provide a collimator and an optical system component using the collimator.

[0008]

SUMMARY OF THE INVENTION A wide band optical fiber collimator 8 of the present invention, which has been made to achieve the above object.
As shown in FIG. 1, reference numeral 18 denotes an optical fiber collimator 8.18 in which a single mode optical fiber 1.11 of a specific wavelength and a lens 4.14 are coupled, and the same optical fiber collimator 8.18 is faced. The coupling loss at this time is the smallest on the shorter wavelength side than the specific wavelength.

As shown in FIG. 1, a wide band optical fiber collimator 8/18 of the present invention made to achieve the above-mentioned object has a single mode optical fiber 1/11 having a wavelength of 1.55 μm and a lens 4/14. The combined optical fiber collimators 8 and 18 have a coupling loss of 1.53 μm when the same optical fiber collimators 8 and 18 face each other.
It is the smallest in m.

The broadband optical fiber collimator 8/18 of the present invention made to achieve the above-mentioned object, as shown in FIG. 1, is a single mode optical fiber 1.1 / having a specific wavelength.
Optical fiber collimator 8 in which 1 and lens 4 and 14 are combined
18 and the positions of the single mode optical fibers 1 and 11 and the lenses 4 and 14 are displaced from the in-focus position by the specific wavelength to the in-focus position on the shorter wavelength side.

As shown in FIG. 1, a wide band optical fiber collimator 8/18 of the present invention made to achieve the above-mentioned object has a single mode optical fiber 1/11 having a wavelength of 1.55 μm and a lens 4/14. Combined optical fiber collimators 8 and 18, which are single mode optical fibers 1
The positions of 11 and the lenses 4 and 14 are arranged at the in-focus position at the wavelength of 1.53 μm.

The broadband optical fiber collimator 8/18 of the present invention made to achieve the above-mentioned object, as shown in FIG. 1, is a single mode optical fiber 1.1 / having a specific wavelength.
1 is an optical fiber collimator in which a lens 4 and a lens 14 are coupled to each other.
The distance from 14 is shifted to the in-focus position at a distance shorter than the in-focus position by the specific wavelength.

As shown in FIG. 1, the optical system component 10 of the present invention made to achieve the above-mentioned object is the same light in which a single mode optical fiber 1/11 having a specific wavelength and a lens 4/14 are coupled. An optical system component 10 in which an optical component 6 is arranged while the fiber collimators 8 and 18 face each other, and the coupling loss when the same optical fiber collimators 8 and 18 face each other is shorter than the specific wavelength. Is the smallest on the side. The optical component 6 is preferably an optical isolator, an optical filter or an optical sensor.

[0014]

In order to minimize the coupling loss when the optical fiber collimators 8 and 18 (see FIG. 1) face each other at a specific wavelength of the single mode optical fibers 1.11, the single mode optical fibers 1.11 and the lens 4 are provided.・ If the position of 14 is adjusted, as shown in FIG.
On the short wavelength side (μm), the coupling loss sharply increases, and on the long wavelength side, the coupling loss becomes small and relatively flat. Therefore, light having a wavelength (1.53 μm) shorter than the specific wavelength is incident on the lenses 4 and 14, and the single mode optical fiber 1 is placed at the position where the condensed light is incident.
By disposing 11., the coupling loss becomes smaller at the wavelengths before and after the specific wavelength.

[0015]

EXAMPLES Examples of the present invention will be described in detail below.

FIG. 1 is a schematic configuration diagram showing an embodiment of a broadband optical fiber collimator 8.18 to which the present invention is applied and a polarization independent optical isolator 10 using the same.

The broadband optical fiber collimators 8 and 18 are
A ferrule 2.12 having a single-mode optical fiber 1.11 for a specific wavelength penetrating the tip end thereof, and a spherical lens 4.1.
The lens holders 5 and 15 to which 4 is adhered and fixed are inserted into the sleeves 3 and 13 and adhered and fixed to be integrated.
The distance between the tip of the single mode optical fiber 1.11, and the spherical lens 414 is such that the light having a wavelength shorter than the specific wavelength is in focus.

In the polarization independent optical isolator 10, the optical isolator 6 is arranged between the wide band optical fiber collimators 8 and 18 facing each other.

The polarization independent optical isolator 10 operates as follows. The light emitted from the single mode optical fiber 1 becomes parallel light by the spherical lens 4 and enters the optical isolator 6. The parallel light that has passed through the optical isolator 6 and is emitted is condensed by the spherical lens 14 and enters the single mode optical fiber 11.

The broadband optical fiber collimator 8 was manufactured as follows.

First, the tip of the single mode optical fiber 1 for wavelength 1.55 μm was inserted into the ferrule 2 made of zirconia to polish the end face, and then a reflection-free coating for wavelength 1.55 μm was applied. The spherical lens 4 was made of optical glass BK7 and had a radius of 1.0 mm, and its surface was coated with a non-reflection coating for a wavelength of 1.55 μm.

The single mode optical fiber 1 and the spherical lens 4 are fixed to a jig on a precision stage, and collimated light with a wavelength of 1.53 μm is emitted from an existing optical fiber collimator. The collimated light is directly irradiated to the end face of the single mode optical fiber 1, and the position and angle of the single mode optical fiber 1 are adjusted so that the display of the optical power meter for measuring the luminous intensity connected to the other end of the single mode optical fiber 1 is maximized. Adjust.

Next, the spherical lens 4 is adhesively fixed to the lens holder 5, the lens holder 5 is inserted and the adhesively fixed sleeve 3 is moved from the front of the ferrule 2, and while the ferrule 2 is being inserted, the collimated light is in single mode. The position is adjusted so that the light is focused on the core of the optical fiber 1. After the position is determined, the ferrule 2 is adhesively fixed to the sleeve 3. A resin adhesive is usually used as an adhesive for fixing the components to each other, and an inorganic adhesive such as low-melting glass is used to improve the environmental resistance, or YAG welding (wavelength 1.06 μm is used). Spot welding of a metal member using a pulsed beam of a YAG laser) may be performed.

The broadband optical fiber collimator 18 is manufactured in the same manner, and the broadband optical fiber collimators 8 and 18 are manufactured.
Face to face at a distance of 2.5 cm. Next, light with a wavelength of 1.49 to 1.58 μm is incident on the single-mode optical fiber 11 to measure the coupling loss. The result is a wavelength of 1.53 μm.
2 is shown as a relative value to the loss at. As shown in the figure, when light with a wavelength of 1.53 μm was incident, it was 0.6 dB, which was the minimum, and it was favorable with 0.5 dB or less in the wavelength width of 1.55 ± 0.03 μm.

For comparison, two optical fiber collimators were manufactured in the same manner as the broadband optical fiber collimators 8 and 18 except that the collimated light having a wavelength of 1.55 μm was used, and the wavelength was set to the single mode optical fiber on the output side. 1.4
The coupling loss was measured by injecting light of 9 to 1.58 μm, and the result is shown in FIG. 3 as a relative value to the loss at the wavelength of 1.55 μm. As shown in the figure, the wavelength is 1.55μ
When the light of m is incident, it becomes a minimum of 0.6 dB, but when it shifts to the short wavelength side, it rapidly increases and the wavelength is 1.54 μm.
When it was made to enter the light, it was as large as 0.86 dB.

In this embodiment, the spherical lenses 4 and 14 are used as the lenses, but even if an aspherical lens or a gradient index lens is used, the broadband light is shifted to the short wavelength side according to the characteristics of each lens. Similar results are obtained by manufacturing a fiber collimator.

[0027]

As described above in detail, the broadband optical fiber collimator manufactured by the method of the present invention has a small coupling loss in a wide wavelength range, and an optical system component using this broadband optical fiber collimator has a wide wavelength range. The performance can be maintained at.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a broadband optical fiber collimator to which the present invention is applied and an optical system component using the same.

FIG. 2 is a diagram showing a relationship between wavelength and coupling loss in an optical system component to which the present invention is applied.

FIG. 3 is a diagram showing the relationship between wavelength and coupling loss in a conventional optical system component.

[Explanation of symbols]

1.11 is a single mode optical fiber, 2.12 is a ferrule, 3.13 is a sleeve, 4.14 is a spherical lens,
5 ・ 15 is a lens holder, 6 is an optical isolator, 8 ・
Reference numeral 18 is a broadband optical fiber collimator, and 10 is a polarization independent optical isolator.

Claims (7)

[Claims] 1. An optical fiber collimator in which a single-mode optical fiber of a specific wavelength and a lens are coupled, and the coupling loss when facing the same optical fiber collimator is minimum on the shorter wavelength side than the specific wavelength. A broadband optical fiber collimator characterized in that 2. An optical fiber collimator in which a single mode optical fiber having a wavelength of 1.55 μm and a lens are coupled to each other, and the coupling loss when the same optical fiber collimator faces each other is minimized at a wavelength of 1.53 μm. Characteristic broadband optical fiber collimator. 3. An optical fiber collimator in which a single-mode optical fiber of a specific wavelength and a lens are coupled, and the positions of the single-mode optical fiber and the lens are on a shorter wavelength side than a focusing position of the specific wavelength. A broadband optical fiber collimator, which is arranged so as to be shifted to a focus position. 4. An optical fiber collimator in which a single mode optical fiber having a wavelength of 1.55 μm and a lens are coupled, and the position of the single mode optical fiber and the lens is arranged at a focus position at a wavelength of 1.53 μm. A broadband optical fiber collimator characterized in that 5. An optical fiber collimator in which a single mode optical fiber of a specific wavelength and a lens are coupled, and the distance between the single mode optical fiber and the lens is shorter than a focusing position by the specific wavelength. A broadband optical fiber collimator, which is arranged so as to be shifted to a focal position. 6. An optical system component in which optical components are arranged while facing the same optical fiber collimator in which a single-mode optical fiber of a specific wavelength and a lens are coupled, and when the same optical fiber collimator is faced. Has a minimum coupling loss on the shorter wavelength side than the specific wavelength. 7. The optical system component according to claim 6, wherein the optical component is an optical isolator, an optical filter or an optical sensor.