JP2004125976A - Optical transmitter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical transmitter capable of easily allocating wavelengths and reducing the space for installation. <P>SOLUTION: Each of the light emitted from a plurality of semiconductor optical amplifying elements 18 of an optical transmitter 1 is introduced into a plurality of optical waveguides 20, and made into light of different wavelengths, respectively, through Bragg diffraction gratings 20a<SB>1</SB>-20a<SB>n</SB>. An optical connector 2 is connected to the optical transmitter 1 by engaging a guide pin in a guide slot 22, and is optically coupled to any of the plurality of optical waveguides 20. Thus, a particular wavelength of light among the wavelengths different from each other is outputted from the optical transmitter 1. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical transmitter.
[0002]
[Prior art]
Conventionally, as shown in FIG. 7, it has been known that communication between the station side 100 and the subscriber side 200 is performed by wavelength-multiplexed optical signals. In this communication system, a plurality of optical transmitters 210 for outputting light of different wavelengths and an optical multiplexer 220 for multiplexing light of these wavelengths are installed on the subscriber side 200, and light of different wavelengths is input. A plurality of optical receivers 110 and an optical demultiplexer 120 for demultiplexing light of these wavelengths are installed on the station side 100.
[0003]
Light from each optical transmitter 210 is multiplexed by an optical multiplexer 220, transmitted through an optical fiber 300, demultiplexed by an optical demultiplexer 120 on the station side 100, and reaches each optical receiver 110. As a result, communication is possible without crosstalk between subscribers.
[0004]
However, this communication method has the following disadvantages. That is, when there is a change in the number of subscribers or the residence of the subscribers, the assignment of the optical signal from the optical transmitter 210 may be changed. Originally, different wavelengths are assigned to optical signals for each subscriber, so if the assignment is changed, the operation becomes very complicated.
[0005]
Therefore, it is conceivable to install a plurality of optical transmitters that output light of different wavelengths in each subscriber's house. FIG. 8 shows an example of a plurality of optical transmitters, and FIG. 9 shows an example of an LD module provided in the optical transmitter. In the optical transmitter 230, when a predetermined current is supplied from the LD driver 231 to the lead pin 232, the laser diode 233 electrically connected to the lead pin 232 emits light. Light from the laser diode 233 is condensed by the condenser lens 234 and output from the LD module 235. The n laser diodes emit light of any wavelength of λ1 to λn. Hereinafter, the difference in wavelength is represented by 1 to n. Light output from the LD module ₂₃₅ 1 _{~ n} is guided to the optical connector ₂₃₇ 1 _{~ n} by the optical fiber ₂₃₆ 1 _{~ n,} is output from the optical connector ₂₃₇ 1 _{~ n} to the outside. For example, the optical transmitters 230 ₁ to 230 _n need to secure a length (α ₁ ) of about 100 mm to accommodate the optical fibers 236 ₁ to 236 _n , and the total length (α ₂ ) is 150 to 150 mm. It becomes 200 mm. The width (β) is 50 to 60 mm.
[0006]
For example, the optical transmitter 230 _m (m-th) is connected to the office 100 via the optical connector 237 _m . Therefore, even if the assignment of the optical signal is changed, the assigned wavelength can be easily set by connecting the optical connector 237 _m of the m-th optical transmitter 230 _m that emits light at a desired wavelength to an external optical fiber. Can be changed.
[0007]
[Problems to be solved by the invention]
However, in the above technique, although the assignment of optical signals is facilitated, a large number of unused optical transmitters 230 ₁ to _n other than the optical transmitter 230 _m actually used for communication are installed in each subscriber's house. Become. Further, if the optical transmitters ₂₃₀ 1 _{~ n} plural installation space for installation of the optical transmitters ₂₃₀ 1 _{~ n} will be taken much.
[0008]
The present invention has been made in view of the above points, and has as its object to provide an optical transmitter capable of easily assigning a wavelength and reducing an installation space.
[0009]
[Means for Solving the Problems]
In order to achieve such an object, an optical transmitter according to the present invention is provided for each of a plurality of semiconductor optical amplifiers and a plurality of semiconductor optical amplifiers, and each partially reflects light of a different wavelength. It is characterized by comprising: a plurality of diffraction gratings; and a fitting portion for positioning and connecting an optical connector so as to output light of a specific wavelength among light transmitted through the plurality of diffraction gratings.
[0010]
According to the present invention, the light generated by each of the plurality of semiconductor optical amplifier elements is converted into laser light having a different wavelength by the plurality of diffraction gratings, and the light having a specific wavelength out of the light having the wavelength is output by the optical connector. Is done. Therefore, by changing the connection position of the optical connector or the optical connector itself, light having a desired wavelength is output from the optical transmitter. In addition, a single optical transmitter can select and output light of a specific wavelength from light of a plurality of wavelengths. Therefore, wavelength allocation is easy and the installation space can be reduced.
[0011]
Further, in the optical transmitter according to the present invention, it is preferable that each of the plurality of diffraction gratings is provided in the optical waveguide. Further, the optical waveguide is preferably a SiO ₂ —GeO ₂ based waveguide formed on a Si substrate or a polymer based waveguide formed on a Si substrate.
[0012]
In the optical transmitter according to the present invention, the space between the plurality of semiconductor optical amplifiers and the optical waveguide is filled with a resin that is optically transparent to light output from the plurality of semiconductor optical amplifiers. Is preferred. In this case, since the plurality of semiconductor optical amplifiers and the optical waveguide are fixed to each other, a positional shift between the plurality of semiconductor optical amplifiers and the optical waveguide is prevented. Therefore, it is possible to avoid a situation in which the light generated by the plurality of semiconductor optical amplifying elements is not introduced into the optical waveguide due to a positional shift.
[0013]
Further, in the optical transmitter according to the present invention, it is preferable that the plurality of semiconductor optical amplifying elements are electrically connected by a lead frame and are molded with resin. Preferably, the fitting portion includes a guide groove into which a guide pin can be inserted.
[0014]
Further, in the optical transmitter according to the present invention, it is preferable that the optical transmitter is in physical contact with the optical connector and optically coupled to the optical connector. In this case, the light output from the optical transmitter is directly input to the optical connector. Thus, optical loss can be reduced as compared with the case where the optical transmitter and the optical connector are connected via a member for connection.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of an optical transmitter according to the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same or corresponding elements will be denoted by the same reference symbols, without redundant description.
[0016]
First, an optical transmitter according to the present embodiment will be described with reference to FIGS. FIG. 1 is a configuration diagram of an optical transmitter according to an embodiment of the present invention, and FIG. 2 is a partially enlarged view of the optical transmitter according to the embodiment of the present invention, where (a) is a plan view. (B) shows a side view, and (c) shows an II end face shown in FIG. 1 (a).
[0017]
The optical transmitter 1 includes a light output unit 12 for emitting and outputting light, and a light output unit 12 that drives the light output unit 12 as necessary to transmit light to the light output unit 12, as shown in FIG. And a driving unit 14 for outputting the same. The light output unit 12, as shown in FIG. 2 (a) ~ (c) , a plurality of semiconductor optical amplifier device 18, a plurality of optical waveguides 20 in which a plurality of Bragg gratings _20a 1 through 20a _n are provided, It has a guide groove 22, a lead frame 24 having lead terminals 24a and 24b, and a Si substrate 26. Further, the plurality of semiconductor optical amplifiers 18, the plurality of optical waveguides 20, the lead frame 24, and the Si substrate 26 are molded with the epoxy resin 16. The housing 10 has a length (x ₁ ) of about 30 mm and a width (y ₁ ) of about 20 mm.
[0018]
The semiconductor optical amplifying element 18 uses, for example, a semiconductor optical amplifying element chip having a double hetero structure of InGaAsP / InP, and is mounted on a first electrode section 28 provided on a Si substrate 26. The first electrode portion 28 is wire-bonded to a lead terminal 24 a extending outside the resin 16. Further, the semiconductor optical amplifier 18 is wire-bonded to the second electrode portion 30, and the second electrode portion 30 is wire-bonded to a lead terminal 24 b extending outside the resin 16. For this reason, a current is supplied to the semiconductor optical amplifying element 18 through the lead terminals 24a and 24b and the bonding wires.
[0019]
Further, the semiconductor optical amplifying element 18 has one end surface serving as a light emitting surface 18a and the other end surface serving as a light reflecting surface 18b. The light reflecting surface 18b is coated, and has a reflectance of 85 to 100%. Therefore, the light emitted from the semiconductor optical amplifier 18 is output from the light emitting surface 18a. Note that a plurality of the semiconductor optical amplifying elements 18 are provided in the optical output unit 12 in parallel.
[0020]
The optical waveguide 20 has a cladding layer of about 10 μm, a core of about 5 to 6 μm square, and a cladding layer of about 10 μm laminated on the Si substrate 26 in this order. The optical waveguide 20 is, for example, an SiO ₂ —GeO ₂ based waveguide or a polymer based waveguide. Further, the optical waveguide 20 is provided such that the tip end surface 20 b thereof faces the light emitting surface 18 a of the semiconductor optical amplifier 18. Therefore, the light emitted from the semiconductor optical amplifier 18 is introduced into the optical waveguide 20. The terminal surface 20 c of the optical waveguide 20 is exposed from the resin 16. The surface on the side where the terminal surface 20c is exposed functions as the light output surface 10a of the optical transmitter 1. The number of the optical waveguides 20 is equal to the number of the semiconductor optical amplifiers 18 provided.
[0021]
A resin 32 is filled between the plurality of semiconductor optical amplification elements 18 and the plurality of optical waveguides 20. This resin 32 is optically transparent to the light output from the semiconductor optical amplifier 18. As the resin 32, for example, a silicone resin or the like can be used.
[0022]
Each optical waveguide 20 is provided with one of a plurality of Bragg gratings _20a 1 through 20a _n. Each Bragg grating 20a ₁ through 20a _n constitutes a resonator with a light reflecting surface 18b of the plurality of semiconductor optical amplifier device 18, each have a different lattice spacing. Thus, each Bragg grating _20a 1 through 20a _n is other Bragg grating _20a 1 through 20a _n are adapted to reflect light partially having a wavelength different from that of light reflected.
[0023]
The guide groove 22 is formed by etching the Si substrate 26. The guide groove 22 is provided for positioning and connecting the optical connector 2 that receives the light output from the light output surface 10a.
[0024]
Here, Si substrate 26 is the length of the mounted in part of the plurality of semiconductor optical amplifier 18 _{(x 2)} is 2 to 3 mm, the length of the mounted in part of the plurality of optical waveguides 20 _{(x 3} ) Is 10 to 15 mm, and the overall length is 12 to 18 mm. The width (y ₂ ) of the light output unit 12 is approximately 14 mm when the number of the semiconductor optical amplifiers 18 is 16, and is approximately 28 mm when the number of the semiconductor optical amplifiers 18 is 32.
[0025]
3A and 3B are configuration diagrams illustrating an example of the optical connector 2 connected to the optical transmitter 1. FIG. 3A is a cross-sectional view, and FIG. 3B is a side view. As shown in FIG. 3, the optical connector 2 sandwiches the optical fiber 3 between a first connector member 2a and a second connector member 2b, and includes a fixing groove 40 for fixing the optical fiber 3 and an optical connector 2. And a guide pin 42 for connecting to the optical output unit 12 of the optical transmitter 1. The fixing groove 40 is formed at a position where the fixed optical fiber 3 is optically coupled to any one of the optical waveguides 20. The guide pin 42 is inserted into the guide groove 22 of the optical transmitter 1. The optical transmitter 1 and the optical connector 2 are connected by inserting and fitting the guide pins 42 into the guide grooves 22.
[0026]
FIG. 4 is a diagram illustrating a state where the optical output unit 12 of the optical transmitter 1 and the optical connector 2 are connected. As shown in FIG. 4, the guide pin 42 is inserted into the guide groove 22, and the optical transmitter 1 and the optical connector 2 are connected in a state of being in physical contact with each other without any other members. The optical fiber 3 fixed in the fixing groove 40 is optically coupled to one of the plurality of optical waveguides 20 and is not optically coupled to the other optical waveguides 20. That is, the optical connector 2 is as entering only light of one wavelength of the plurality of Bragg gratings 20a ₁ through 20a _n different wavelengths of light transmitted through the.
[0027]
Next, the operation of the optical transmitter 1 will be described. First, a current is supplied from the drive unit 14 to each semiconductor optical amplifying element 18. Thereby, each semiconductor optical amplifying element 18 emits light. This light is not emitted from the light reflection surface 18b having a high reflectance, but is emitted from the light emission surface 18a.
[0028]
The light emitted from the light emitting surface 18a toward the optical waveguide 20 passes through the optically transparent resin 32 and enters the optical waveguide 20 with respect to the light. Light incident on the optical waveguide 20 is partially reflected by the guided Bragg gratings _20a 1 through 20a _n. The reflected light returns to each semiconductor optical amplifier 18 and is reflected by the light reflecting surface 18b. By this reflection is repeated, light is amplified by the laser oscillation is transmitted through the Bragg gratings 20a ₁ through 20a _n. Light transmitted herein have the predetermined lasing wavelength determined by the lattice spacing of the Bragg grating _20a 1 through 20a _n. Since the Bragg grating 20a ₁ through 20a _n are set to different lattice spacing, light laser oscillation will have a different wavelengths.
[0029]
Each of the transmitted lights reaches the end surface 20c of the optical waveguide 20. Since the optical connector 2 is optically coupled to only one of the plurality of optical waveguides 20, not all of the light that has reached the termination surface 20c is output to the optical connector 2; Only the signal is output to the optical connector 2.
[0030]
As described above, in the optical transmitter 1 according to this embodiment, light generated by each of the plurality of semiconductor optical amplifier 18, respectively laser oscillation light of different wavelengths by a plurality of Bragg gratings 20a ₁ through 20a _n Then, the optical connector 2 outputs light of a specific wavelength among the lights of those wavelengths. Therefore, by changing the connection position of the optical connector 2 or the optical connector 2 itself, light of a desired wavelength is output from the optical transmitter 1. In addition, a single optical transmitter 1 can select and output light of a specific wavelength from light of a plurality of wavelengths. Therefore, wavelength allocation is easy and the installation space can be reduced. In addition, since the semiconductor optical amplifier 18 and the optical waveguide 20 are formed integrally on the same substrate, the optical transmitter 1 is downsized.
[0031]
Further, in the optical transmitter 1 according to the present embodiment, since the plurality of semiconductor optical amplifiers 18 and the optical waveguide 20 are fixed to each other, positional deviation between the plurality of semiconductor optical amplifiers 18 and the optical waveguide 20 is prevented. Will be done. Therefore, it is possible to avoid a situation in which the light generated by the plurality of semiconductor optical amplifying elements 18 is not introduced into the optical waveguide 20 due to a positional shift.
[0032]
In the optical transmitter 1 according to the present embodiment, light output from the optical transmitter 1 is directly input to the optical connector 2. Thereby, light loss can be reduced as compared with the case where the optical transmitter 1 and the optical connector 2 are connected via a connecting member.
[0033]
Next, a modified example of the optical transmitter 1 according to the present embodiment will be described. FIG. 5 is a configuration diagram illustrating a modified example of the optical output unit 12 of the optical transmitter 1 according to the present embodiment.
[0034]
As shown in FIG. 5, in the optical output unit 12 of the present modification, a plurality of semiconductor optical amplifiers 50 are formed on the same chip. It is not necessary to mount a plurality of semiconductor optical amplifier elements 50 individually, and thus the electrode section 52 is not provided in a plural number, but is formed as a single electrode section. Accordingly, the number of bonding wires has been reduced. Each semiconductor optical amplifying element 50 is formed so as to face the plurality of optical waveguides 20, and light is introduced into the optical waveguides 20 similarly to the one shown in FIG.
[0035]
As described above, also in the present modification, as in the embodiment shown in FIGS. 1 to 4, the wavelength allocation is easy, the installation space can be reduced, and the generation occurs in a plurality of semiconductor optical amplifiers 50. It is possible to avoid a situation in which light is not introduced into the optical waveguide 20 due to a positional shift, and it is possible to reduce optical loss as compared with a case where light is transmitted through a member for connecting the optical transmitter 1 and the optical connector 2. .
[0036]
Further, in the present modification, since the plurality of semiconductor optical amplifiers 50 are formed on the same chip, the number of electrode portions 52 on which the semiconductor optical amplifiers 50 are mounted and the number of bonding wires can be reduced. In this modification, the optical transmitter 1 is also downsized.
[0037]
Next, a modified example of the optical connector 2 will be described. 6A and 6B are configuration diagrams showing a modification of the optical connector 2, wherein FIG. 6A is a cross-sectional view, and FIG. 6B is a side view.
[0038]
As shown in FIG. 6, the optical connector 2 of this modification also sandwiches the optical fiber 3 between the first connector member 2a and the second connector member 2b. Both connector members 2a and 2b have a Si substrate 60 and a cavity 62. In the state where the optical fiber 3 is sandwiched, only one side surface of the Si substrate 60 is exposed to the outside. The exposed surface is in physical contact with the optical transmitter 1. The Si substrate 60 is provided with a fixing groove 64 formed by etching to fix the optical fiber 3. The fixing groove 64 extends from the side surface opposite to the exposed surface of the Si substrate 60 toward the exposed surface, and is formed at a position where the fixed optical fiber 3 is optically coupled to any one of the optical waveguides 20. . The cavity 62 is formed in both connector members 2a and 2b as a space for guiding the optical fiber 3 to the fixing groove 64.
[0039]
The optical connector 2 is connected to the optical transmitter 1. However, if the connection is not appropriate, that is, if the fixing groove 64 is displaced, the optical loss incurred when light is introduced from the optical waveguide 20 to the optical fiber 3 increases. Would. However, in the optical connector 2 of this modified example, since the fixing groove 64 is formed by etching, the position is accurate.
[0040]
As described above, also in the optical connector 2 of the present modified example, the optical connector 2 can be connected to the optical transmitter 1 similarly to the optical connector 2 shown in FIG. Further, in the optical connector of the present modified example, light loss at the connection location can be reduced.
[0041]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to provide an optical transmitter capable of easily assigning a wavelength and reducing an installation space.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an optical transmitter according to the present embodiment.
FIGS. 2A and 2B are partially enlarged views of the optical transmitter according to the present embodiment, in which FIG. 2A is a plan view, FIG. 2B is a side view, and FIG. FIG. 1 (a) shows an II end face.
FIGS. 3A and 3B are configuration diagrams illustrating an example of an optical connector connected to the optical transmitter according to the embodiment, in which FIG. 3A is a cross-sectional view and FIG. 3B is a side view.
FIG. 4 is a diagram illustrating a state where an optical output unit of an optical transmitter and an optical connector are connected.
FIG. 5 is a configuration diagram illustrating a modified example of the optical output unit of the optical transmitter according to the present embodiment.
6A and 6B are configuration diagrams showing a modification of the optical connector 2, wherein FIG. 6A is a cross-sectional view and FIG. 6B is a side view.
FIG. 7 is a configuration diagram schematically illustrating a wavelength division multiplexing communication system.
FIG. 8 is a configuration diagram illustrating an example of a conventional optical transmitter.
FIG. 9 is a configuration diagram illustrating an example of an LD module in a conventional optical transmitter.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Optical transmitter, 2 ... Optical connector, 3 ... Optical fiber, 12 ... Optical output part, 14 ... Drive part, 16 ... Resin, 18, 50 ... Semiconductor optical amplification element, 18a ... Light emission surface, 18b ... Light reflection surface, 20 ... optical _waveguide, 20a 1 through 20a n _... Bragg grating, 22 ... guide groove, 24 ... lead frame, 26 ... Si substrate, 32 ... resin, 40, 64 ... fixing groove, 42 ... guide pin, 60 ... Si substrate, 62 ... hollow part.

Claims (8)

A plurality of semiconductor optical amplifiers;
A plurality of diffraction gratings provided for each of the plurality of semiconductor optical amplification elements, each partially reflecting light of a different wavelength,
A fitting portion for positioning and connecting the optical connector so as to output light of a specific wavelength among the lights transmitted through the plurality of diffraction gratings,
An optical transmitter, comprising: The optical transmitter according to claim 1, wherein each of the plurality of diffraction gratings is provided in an optical waveguide. The optical waveguide, an optical transmitter according to claim 2, characterized in that the SiO ₂ -GeO ₂ Keishirube waveguide formed on a Si substrate. The optical transmitter according to claim 2, wherein the optical waveguide is a polymer-based waveguide formed on a Si substrate. 3. A resin between the plurality of semiconductor optical amplifiers and the optical waveguide is filled with a resin which is optically transparent to light output from the plurality of semiconductor optical amplifiers. The optical transmitter according to any one of claims 4 to 4. The optical transmitter according to claim 1, wherein the plurality of semiconductor optical amplifying elements are electrically connected by a lead frame and are molded with a resin. The optical transmitter according to claim 1, wherein the fitting portion includes a guide groove into which a guide pin can be inserted. The optical transmitter according to any one of claims 1 to 7, wherein the optical transmitter is in physical contact with the optical connector and optically coupled to the optical connector.

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