JPH05136486A - Ic chip for light amplification - Google Patents

Abstract

PURPOSE:To obtain an IC chip for light amplification, which is excellent in productivity and reliability, and have possibilities for its smaller size and lighter weight. CONSTITUTION:An optical fiber for amplification is arranged on a single chip substrate 2 by being fused and integrated with a glass layer. While at the same time, waveguides 10, 12, a light-mixing section, and a mixing light waveguide are formed at the irradiated end of an optical fiber for amplification. More concretely, the waveguide takes in a signal light and an exciting light respectively. The light-mixing section 14 mixes the signal light and the exciting light consecutively coming from these waveguides. The mixing light waveguides 16 gets to an optical fiber 4 for amplification by being guided consecutively from the light-mixing section. On the other hand, an amplified light waveguides 18 to guide out amplified light is formed at the emitting end of the optical fiber 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical amplification IC chip formed by integrating an amplification optical fiber doped with a rare earth element on a chip substrate.

[0002]

2. Description of the Related Art Conventionally, an optical amplifier for amplifying signal light by utilizing the stimulated emission effect of an amplification optical fiber doped with a rare earth element is an optical fiber for transmitting signal light, an optical fiber for introducing pumping light, An optical multiplexer that mixes signal light and pumping light, an amplification optical fiber, a filter that extracts only signal light from the amplified light, and a transmission optical fiber that guides light that has passed through this filter are sequentially arranged. .. That is, the conventional optical amplifier is configured by combining separate optical devices.

However, when the optical amplifier is constructed by simply gathering the separate and independent optical devices in this way, not only the overall shape of the optical amplifier becomes large, but also the weight becomes considerably heavy, and the cost is increased. However, it is disadvantageous in handling.

Therefore, the present inventors have provided an optical amplifier as shown in FIG. 5 (see Japanese Patent Application No. 406990/1990).

This optical amplifier comprises an optical IC chip A and a long amplification optical fiber B externally connected to the optical IC chip A. The optical IC chip A is a single glass chip substrate. On a, optical waveguides b and c for introducing signal light and pumping light from the outside, an optical multiplexer d for mixing signal light and pumping light from the respective waveguides b and c, and an optical multiplexer d A waveguide e for guiding the derived mixed light to the amplification optical fiber B, a waveguide g for introducing the amplified light amplified by the amplification optical fiber B, and a signal light and a pumping light from the amplification light. Optical demultiplexing parts h for demultiplexing are integrally formed.

In this optical amplifier, the amplifying optical fiber B is externally connected to the optical IC chip A because the technical level at the time of development of this optical amplifier is
A rare earth element (for example, Er) is added to the amplification optical fiber B.
This is because it is difficult to dope with a high concentration, and in order to obtain the required amplification factor, the length of the amplification optical fiber B must be long.

[0007]

In the optical amplifier shown in FIG. 5, the optical amplifier is smaller and lighter in weight and has higher productivity and reliability as compared with the conventional optical amplifier which is formed by simply gathering separate and independent optical devices. Can be expected.

However, as described above, if the amplification optical fiber B is externally connected to the optical IC chip A,
Not only is it difficult to miniaturize, but there are many parts where the optical fibers are butted and connected to the optical IC chip A (in this example, the optical fibers are butted and connected to the waveguides b, c, e, and g, respectively). Therefore, the total number of connection parts is 5).

In recent years, if the technical level is increased and it becomes possible to dope a rare earth element to a high concentration (for example, about 10000 ppm), a required amplification factor can be obtained even with a short amplification optical fiber.

Therefore, it is conceivable to install a short amplification optical fiber on the chip substrate and connect it to the waveguide to achieve miniaturization. For that purpose, for example, the amplification optical fiber is mounted on the chip substrate a. When fixed with an adhesive,
Since the thermal expansion coefficient of the adhesive is greatly different from that of the amplification optical fiber or the chip substrate a, when subjected to a thermal cycle, the amplification optical fiber and the waveguide are different due to the difference in the thermal expansion coefficients. There will be problems such as the deviation of the optical axis of the adhesive and the peeling of the adhesive.

[0011]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and is an IC for optical amplification, which is smaller and lighter than conventional ones, and is expected to have high productivity and reliability. It is to get the chips.

Therefore, the optical amplification IC chip of the present invention comprises a single chip substrate on which the amplification optical fiber is fused and integrated by the glass layer and the amplification is performed. A signal optical waveguide and a pumping optical waveguide that introduce the signal light and the pumping light from the outside to the incident end side of the optical fiber for use, respectively While forming an optical multiplexing part and a mixed optical waveguide that is sequentially derived from the optical multiplexing part and reaches the amplification optical fiber, the amplified light is derived on the emission end side of the amplification optical fiber. It is characterized in that an amplifying optical waveguide is formed.

[0013]

In the above structure, the signal light and the pumping light introduced from the outside pass through the respective waveguides, the both lights are mixed in the optical combining section, and the mixed light passes through the waveguides and is fed into the amplification optical fiber. Will be introduced to. Since the amplification optical fiber amplifies the signal light based on the stimulated emission effect of the rare earth element by the excitation light, the amplified light is extracted through the waveguide.

Here, all the optical devices including the amplification optical fiber and the waveguides connecting the devices are formed in a state of being integrated on a single chip substrate.
Since the amplification optical fiber is fused and integrated, peeling,
Compact and lightweight with high productivity without fear of optical axis deviation.
Reliability can be expected.

[0015]

FIG. 1 is a plan view of an optical amplification IC chip according to this embodiment, FIG. 2 is a sectional view taken along the line AA of FIG. 1, and FIG. 3 is a sectional view taken along the line BB of FIG. Is.

In these figures, reference numeral 1 is an I for optical amplification.
The entire C chip is shown, 2 is a quartz glass-based chip substrate, and 4 is an amplification optical fiber.

The amplification optical fiber 4 amplifies the signal light based on the stimulated emission effect of the rare earth element by the excitation light, and the inside of the core 4a of the silica optical fiber is obtained so that a required amplification factor can be obtained. Alternatively, the outer peripheral surface portion of the core 4a in contact with the clad 4b is doped with a predetermined amount of a rare earth element. For example, for core 4a, Er is 100 to
Doping is performed at a concentration of about 10,000 ppm.

A groove 6 having, for example, a V shape or a U shape is formed in advance on the chip substrate 2 and the groove 6 is formed.
The amplification optical fiber 4 is arranged in the optical fiber, and the glass layer 8 is fused and integrated on the outer periphery of the amplification optical fiber 4. The glass layer 8 is formed, for example, after the soot is deposited on the outer circumference of the amplification optical fiber 4 and the chip substrate 2,
It is obtained by vitrifying this soot. In this case, the components and the addition amount of the soot are adjusted in advance so that the amplification optical fiber 4 is not adversely affected.

As described above, the amplification optical fiber 4 is firmly fixed by the glass layer 8 around the amplification optical fiber 4, and the chip substrate 2 and the glass layer 8 have substantially the same coefficient of thermal expansion. It is extremely stable and there is no risk of aging.

On the incident end side of the amplification optical fiber 4,
A signal optical waveguide 10 for introducing signal light of a single wavelength (for example, 1.55 μm wavelength band), a predetermined wavelength (for example, 1.48 μm)
A pumping optical waveguide 12 for introducing pumping light in the (μm wavelength band) from the outside, and an optical multiplexing section 1 for mixing the signal light and the pumping light by mode coupling by arranging the respective waveguides 10, 12 in close proximity to each other.
4 and a mixed optical waveguide 16 that guides the mixed light from the optical multiplexer 14 to the amplification optical fiber 4.

On the other hand, on the output end side of the amplification optical fiber 4, an amplification optical waveguide 18 for guiding the light amplified by the amplification optical fiber 4, and the amplification light from the amplification optical waveguide 18 is excited as signal light. An optical demultiplexing section 20 for demultiplexing into light and a signal optical waveguide 2 for deriving the signal light demultiplexed by the optical demultiplexing section 20.
2 and pumping optical waveguides 24 that guide the demultiplexed pumping light are formed.

Each of these waveguides 10, 12, 16, 1
Since 8, 22, and 24 are manufactured by etching,
It has a rectangular cross section, and each waveguide 10, 12, 1
6, 18, 22, and 24, the optical multiplexing unit 14, and the optical demultiplexing unit 20 are all covered with the glass layer 8 similarly to the amplification optical fiber 4. Furthermore, the optical axes of the mixed optical waveguide 16 and the amplification optical waveguide 18 are aligned with the core 4a of the amplification optical fiber 4, and the abutting end faces of the waveguides 16 and 18 and the amplification optical fiber 4 are made of a glass layer. 8 are fused together when heated to form 8.

The optical fiber 2 is provided for each of the waveguides 10, 12, 22 facing the left and right end surfaces of the chip substrate 2.
6 are connected in a butted state. Here, the connection of the optical fiber 26 to the optical amplification IC chip 1 is
There are a total of three locations, and the connection loss is reduced by the number of connection locations as compared with the case of the conventional example shown in FIG.

In the optical amplification IC chip 1 having the above structure, the signal light and the pump light introduced from the optical fiber 26 are
Each propagates through the signal optical waveguide 10 and the pumping optical waveguide 12, and reaches the optical multiplexer 14. Then, the signal light and the pumping light are mixed in the optical multiplexer 14, and the mixed light propagates through the mixed optical waveguide 16 and is guided into the amplification optical fiber 4.

In the amplification optical fiber 4, the signal light is amplified based on the stimulated emission effect of the rare earth element (for example, Er ion) by the excitation light, and the amplified light passes through the amplification optical waveguide 18 and is divided into optical components. The wave portion 20 demultiplexes the signal light into the excitation light and the amplified signal light, and the amplified signal light is guided from the signal optical waveguide 22 to the optical fiber 26.

In the above embodiment, the waveguides 10, 12, 22 are directly exposed to the left and right end surfaces of the chip substrate 2, but in this case, the waveguides 10, 12, 22 are provided.
The cross section of the waveguide is rectangular, while the waveguides 10, 12, 22
Since the cross-sectional shape of the core of the optical fiber 26 that is butt-connected to each other is circular, there is still a degree of splice loss which is still present when such different dimensional shapes are simply butted.

To improve this, as shown in FIG.
On the chip substrate 2, an auxiliary optical fiber 28 is provided corresponding to each of the waveguides 10, 12, 22 and one end of this auxiliary optical fiber 28 is connected to the waveguides 10, 12, 22 and the other one is connected. The end is exposed to the end face of the chip substrate 2, and the optical fiber 26 is butted and connected to the auxiliary optical fiber 28 from the outside. In this case, at one end of the auxiliary optical fiber 28, the core has its optical axis aligned with the waveguides 10, 12, and 22, and the abutting end face thereof is heated to form the glass layer 8. At this time, since the circular cores are butted against each other at the other end of the auxiliary optical fiber 28 to which the optical fiber 26 is connected and are fused together, the overall connection loss is Figure 1
Less than in the case of the configuration.

Further, in the above embodiment, the optical demultiplexing section 20 is provided, but instead of this, a bandpass filter is provided on the chip substrate 2 so that only the signal light after amplification is taken out. Good. In addition, an optical branching portion for branching the amplified signal light into a plurality of paths and emitting the branched light is provided as a signal optical waveguide 2.
It is also possible to form them on the chip substrate 2 in a state of being serialized with 2. Further, antireflection coating (non-reflection coating) is applied to each of the left and right end surfaces of the chip substrate 2 to which the optical fiber 26 is connected in order to prevent laser oscillation in each waveguide and the amplification optical fiber 4. Is more preferable.

[0029]

According to the present invention, all the optical devices including the above-mentioned amplification optical fiber and the waveguides connecting the devices are formed in an integrated state on a single chip substrate, and the amplification is performed. Since the optical fibers for fusion are integrated by fusion, it is possible to achieve significantly smaller size and weight compared to the conventional example in which each individually configured single large component is simply assembled. Very high productivity and high reliability can be achieved in its manufacture.

[Brief description of drawings]

FIG. 1 is a plan view of an optical amplification IC chip according to the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a sectional view taken along line BB of FIG.

FIG. 4 is a plan view of an optical amplification IC chip showing a modification of the present invention.

FIG. 5 is a plan view showing an outline of a conventional optical amplifier.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... IC chip for optical amplification, 2 ... Chip substrate, 4 ... Optical fiber for amplification, 8 ... Glass layer, 10 ... Signal optical waveguide, 12
... excitation optical waveguide, 14 ... optical multiplexing section, 16 ... mixed optical waveguide, 18 ... amplification optical waveguide.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masataka Nakazawa 1-6, Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation (72) Yasuro Kimura 1-6-1, Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation

Claims (1)

[Claims] 1. A single chip substrate (2) is provided on which a glass optical layer (4) for amplification is provided.
A signal optical waveguide (10) for introducing signal light and pumping light from the outside while being fused and integrated by (8) and arranged on the incident end side of the amplification optical fiber (4).
And the excitation optical waveguide (12) and these signal optical waveguides (1
0) and the pumping optical waveguide (12), and an optical multiplexer (14) for mixing the signal light and the pumping light, and this optical multiplexer.
The amplification optical fiber, which is successively derived from (14)
A mixed optical waveguide (16) reaching (4) is formed, while an amplification optical waveguide (18) for guiding amplified light is formed on the emission end side of the amplification optical fiber (4). An optical amplification IC chip characterized by: