JP2003264513A - Two-way optical communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical communication system capable of two-way optical communication through one single core optical fiber by small and compact optical signal transmitter/receivers. <P>SOLUTION: In this optical communication system 30, one transmitting/receiving side and the other transmitting/receiving side are respectively provided with a first optical signal transmitter/receiver 32 and a second optical signal transmitter/receiver 34, and two-way optical communication is performed between the first optical signal transmitter/receiver 32 and the second optical signal transmitter/receiver 34 through the one signal core optical fiber 36. The first optical signal transmitter/receiver is provided with a first VCSEL (vertical cavity surface-emitting laser) 38 for emitting an optical signal of first wavelength, and a first PD (phase change rewritable disk) 40 provided and optically coupled onto the first VCSEL, optically coupled to one end part of the optical fiber and for receiving an optical signal of second wavelength shorter than the first wavelength. The second optical signal transmitter/receiver is provided with a second PD 42 for receiving the optical signal of first wavelength, and a second VCSEL 44 provided and optically coupled onto the second PD, optically coupled to the other end part of the optical fiber and for emitting the optical signal of second wavelength. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical communication system capable of bidirectional communication between one transmission / reception side and the other transmission / reception side, and more particularly, via a single optical fiber. The present invention relates to an optical communication system in which two-way optical communication is possible and a small optical signal transmitting / receiving device is provided on one transmitting / receiving side and the other transmitting / receiving side.

[0002]

2. Description of the Related Art In an optical communication system, as shown in FIG. 4, basically, light emitted from a light emitting element such as a semiconductor laser element or a light emitting diode modulated by an electric signal on the transmitting side is used as an optical signal in an optical fiber. To the receiver via
On the receiving side, the transmitted optical signal is transferred to the photodiode (P
D, a photodetector) and the like to detect and demodulate as an electric signal. Then, in order to perform bidirectional optical signal transmission / reception between one side and the other side, an optical signal transmitting device having a light emitting element and an optical signal receiving device having a photodiode are provided on both sides, respectively. Transmission and reception using a two-core optical fiber that connects the optical signal transmitter on one side and the optical signal receiver on the other side, and connects the optical signal transmitter on the other side and the optical signal receiver on one side It is carried out.

The configuration of a conventional bidirectional optical communication system will be specifically described with reference to FIG. FIG. 5 is a schematic diagram showing a configuration of a conventional bidirectional optical communication system. As shown in FIG. 5, a conventional bidirectional optical communication system 10 basically includes a first optical signal transmitting / receiving apparatus 12 provided on one transmitting / receiving side and a first optical signal transmitting / receiving apparatus 12 provided on the other transmitting / receiving side. Two optical signal transmitting / receiving apparatus 14 and one core or two cores connecting the first and second optical signal transmitting / receiving apparatus 12, 14
It is composed of first and second optical fibers 16A and 16B.

The first optical signal transmitter / receiver 12 is optically coupled to one end of the first optical fiber 16A, and transmits an optical signal via the first optical fiber 16A. Device (hereinafter referred to as VCSEL),
A first optical signal transmitter 18 having a driving device (not shown) for driving the VCSEL, and a second optical fiber 16B.
A GaAs-based photodiode that is optically coupled to one end of the second optical signal transmitter 24 and receives an optical signal transmitted from a second optical signal transmitter 24 described below via a second optical fiber 16B and converts the optical signal into an electrical signal ( Hereinafter, the first optical signal receiving device 20 having a PD will be provided. The second optical signal receiver 14 is optically coupled to the other end of the first optical fiber 16A and receives the optical signal transmitted from the first optical signal transmitter 18 via the first optical fiber 16A. A second optical signal receiving device 22 having a GaAs-based PD that receives light and converts it into an electrical signal is optically coupled to the other end of the second optical fiber 16B, and an optical signal is transmitted via the second optical fiber 16B. And a drive device (not shown) for driving the VCSEL, and a second optical signal transmission device 24 for transmitting an optical signal.

[0005]

However, in the conventional bidirectional optical communication system, as described above, the two-core optical fiber is required, and the VCSEL and PD as the optical signal transmitting / receiving devices are provided on both sides. Since it is necessary to arrange them in parallel, the optical signal transmitter / receiver becomes large. With this, it is difficult to apply the conventional bidirectional optical communication system to the field of bidirectional optical communication between individuals, which is expected to develop in the future. Therefore, an object of the present invention is to provide an optical communication system capable of bidirectional optical communication via a single optical fiber by a small and compact optical signal transmitting / receiving apparatus.

[0006]

In order to achieve the above object, an optical communication system according to the present invention comprises first and second optical signal transmission / reception devices on one transmission / reception side and the other transmission / reception side, respectively. An optical communication system for performing bidirectional optical communication between a first optical signal transmitting / receiving device and a second optical signal transmitting / receiving device via a single optical fiber, wherein the first optical signal transmitting / receiving device is
A first surface-emitting light-emitting device that emits an optical signal of a first wavelength and a compound semiconductor layer having an absorption edge wavelength shorter than the first wavelength and are optically coupled onto the first surface-emitting light-emitting device. And is optically coupled to one end of the optical fiber.
First light-transmitting optical signal emitted from the surface-emitting type light-emitting element is incident on the optical fiber, and at the same time, the optical signal having a second wavelength shorter than the absorption edge wavelength is received through the optical fiber.
And a light receiving element of
A second light receiving element for receiving an optical signal having a wavelength of, and a compound semiconductor layer having an absorption edge wavelength shorter than the first wavelength, provided optically coupled to the second light receiving element, and It is optically coupled to the other end and transmits the optical signal of the first wavelength received through the optical fiber to reach the second light receiving element and emits the optical signal of the second wavelength through the optical fiber. And a second surface-emitting type light emitting element that

In the first optical signal transmitter / receiver on the transmitting / receiving side, the first light receiving element is composed of a compound semiconductor layer having an absorption edge wavelength shorter than the first wavelength, and a second wavelength shorter than the absorption edge wavelength. The wavelength of the optical signal that receives the light and is emitted from the first surface-emitting light emitting device, that is, the first wavelength, is longer than the absorption edge wavelength of the compound semiconductor that constitutes the first light receiving device.
As a result, the optical signal emitted from the first surface-emitting light emitting element is transmitted to the second optical signal transmitting / receiving device through the optical fiber while being hardly absorbed by the first light receiving element.
The optical signal of the first wavelength transmitted to the second optical signal transmitting / receiving device is almost absorbed by the second surface-emitting light emitting device that emits the optical signal of the second wavelength by the same mechanism as described above. Without passing through, it reaches the second light receiving element that receives the optical signal of the first wavelength, is received, and is converted into an electrical signal.

In the second transmitting / receiving side optical signal transmitting / receiving device, the optical signal of the second wavelength emitted from the second surface emitting light emitting element is transmitted to one transmitting / receiving side through the optical fiber. It The second transmitted from the second optical signal transmitter / receiver
The optical signal of the second wavelength receives the optical signal of the second wavelength
Is received by the light receiving element and converted into an electric signal.

In a preferred embodiment of the present invention, each of the first and second optical signal transmitting / receiving devices is constructed as a module in which a surface emitting light emitting element and a light receiving element are integrally optically coupled. The module may be a monolithic module or a hybrid type module.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described specifically and in detail with reference to the accompanying drawings. Embodiment Example This embodiment example is an example of an embodiment of a bidirectional optical communication system according to the present invention, and FIG. 1 is a schematic diagram showing a configuration of an optical communication system of the present embodiment example. The optical communication system 30 of the present embodiment example includes a first optical signal transmitting / receiving device 32 and a second optical signal transmitting / receiving device 34 on one transmitting / receiving side and the other transmitting / receiving side, respectively, and the first optical signal transmitting / receiving device 3
The optical communication system performs bidirectional optical communication via a single optical fiber 36 provided between the second optical signal transmitting / receiving device 34 and the second optical signal transmitting / receiving device 34.

The first optical signal transmitter / receiver 32 has a first surface emitting semiconductor laser element (hereinafter referred to as VCSEL) 38 for emitting an optical signal of a first wavelength and an absorption edge wavelength of a first wavelength. First VC composed of compound semiconductor shorter than wavelength
The optical fiber 3 is provided on the SEL 38 by optical coupling.
6, a first photodiode (hereinafter, referred to as PD) 40 that is optically coupled to one end of the 6 and receives an optical signal of a second wavelength shorter than the absorption edge wavelength.

The first VCSEL 38 has an oscillation wavelength of 1.
It is a GaInNAs VCSEL of 3 μm to 1.55 μm, and therefore the optical signal of the first wavelength has a wavelength of 1.3 μm.
It is an optical signal in the range of ˜1.55 μm.

The first PD 40 is a GaAs-based pin photodiode made of a GaAs-based compound semiconductor. As will be described later, the first PD 40 has a first VCSEL 38 as an electrode on the back surface of the substrate. A circular window is opened so that the optical signal emitted from the device passes through. The wavelength corresponding to the band gap energy (1.43 eV) of GaAs forming the first PD 40, that is, the absorption edge wavelength is 0.88 μm, and the first VCSEL3
The first wavelength of the optical signal emitted from 8 is 1.3 μ
Since it is shorter than the wavelength in the range of m to 1.55 μm,
The PD 40 transmits the optical signal emitted from the first VCSEL 38 without being absorbed in the first PD 40 and allows the optical signal to enter the optical fiber 36, while the first PD 40 has the second wavelength shorter than the absorption edge wavelength. , For example, an optical signal of 0.85 μm is received. First VCSEL 38 and first PD 40
And are configured as a module that is optically coupled together.

The second optical signal transmitter / receiver 34 is a second PD composed of an InGaAs compound semiconductor provided on the InP substrate so as to receive the optical signal of the first wavelength.
42, and a GaAs-based surface-emitting semiconductor laser device that is optically coupled to the second PD 42 and is optically coupled to the other end of the optical fiber 36 to emit an optical signal of the second wavelength. And a second VCSEL 44. still,
In FIG. 1, the positional relationship between the second PD 42 and the second VCSEL 44 is shown upside down for convenience. By the same mechanism as described above, the optical signal of the first wavelength is transmitted through the GaAs-based compound semiconductor forming the second VCSEL 44 without being absorbed, and the second PD is transmitted.
It reaches 42 and is received. First PD 42 and second V
CSEL44 is a monolithic optical
It is organized as a module. The module is
The module is not limited to monolithic and may be a hybrid type module.

With the above configuration, in the bidirectional optical communication system 30 of this embodiment, the first optical signal transmitting / receiving device 32 is used.
The optical signal emitted from the first VCSEL 38 of
The optical fiber 3 is transmitted without being absorbed by the PD 40.
6, and reaches the second optical signal transmitter / receiver 34 via the optical fiber 36. The optical signal that has reached the second optical signal transmission / reception device 34 passes through the second VCSEL 44 and is received by the second PD 42. Second optical signal transmitter / receiver 3
The optical signal emitted from the second VCSEL 44 of No. 4 enters the optical fiber 36 and reaches the first optical signal transmitter / receiver 32 via the optical fiber 36. The optical signal that reaches the first optical signal transmitting / receiving device 32 is received by the first PD 40.

In the present embodiment, the first VCSEL 38
Is composed of a GaInNAs-based compound semiconductor,
It may be composed of an InGaAsP-based compound semiconductor.

Here, the configurations of the first and second optical signal transmitting / receiving devices 32 and 34 will be described with reference to FIGS. 2A and 2B are a cross-sectional view and a plan view showing the configuration of the first optical signal transmitting / receiving apparatus, and FIGS. 3A and 3B show the configuration of the second optical signal transmitting / receiving apparatus. FIG. 3 is a cross-sectional view and a plan view showing As shown in FIG. 2A, the first optical signal transmitter / receiver 32 includes a first VCSEL 38 and a first VCSEL 38.
First PD optically coupled to the VCSEL 38 of
40 and.

The first VCSEL 38 is a GaInNAs
2A, which is a surface-emitting type semiconductor laser device of a system, as shown in FIG.
And a pair of multi-layered film reflecting mirrors 48A and 48B sandwiching the upper and lower sides of the light-emitting layer 52 having an active layer 50 and the multi-layered film reflecting mirror
8B is provided with a p-side electrode 56 provided via a contact layer 54, and an n-side electrode 58 provided on the back surface of the n-GaAs substrate 46. Further, the p-side electrode 56 is provided with a circular window 60 for transmitting an optical signal. First P
D40 is a GaAs-based pin photodiode, and as shown in FIGS.
Ga provided on the substrate 62 and having an i-layer active layer 64
An As-based light receiving layer 66 and a p-side electrode 68 provided on the light receiving layer 66 are provided. Further, the p-side electrode 68 is provided with a circular window 70 for transmitting an optical signal.

The n-side electrode of the first PD 40 is connected to the first VC
It is a common electrode with the p-side electrode 56 of the SEL 38. Further, the common electrode 56 has a first PD as a lead electrode.
A contact plug 72 that penetrates through the layer structure of 40 and is electrically connected to the common electrode 56 is provided via an insulating film 74 between the contact plug 72 and the layer structure. By providing a lead wire to the contact plug 72, a current is injected between the p-side electrode (common electrode) 56 and the n-side electrode 58 of the first VCSEL 38, and the p-side electrode 68 and n of the first PD 40 are connected. It is possible to easily draw a current from between the side electrode (common electrode) 56.

The second optical signal transmitter / receiver 34 is shown in FIG.
As shown in (a) and (b), the second PD 42 is optically coupled to the second PD 42 on the second PD 42.
L44 and. The second PD 42 is an InGaAs-based pin photodiode. As shown in FIG. 3A, the second PD 42 is provided on the n-InP substrate 76 and an InGaAs-based light-receiving layer 80 having an i-layer active layer 78. , Light-receiving layer 8
0 and the p-side electrode 82 and the n-InP substrate 76
And an n-side electrode 84 provided on the back surface of the. A circular window 86 for transmitting an optical signal is formed in the p-side electrode 82.
Is provided.

The second VCSEL 44 is a GaAs surface-emitting type semiconductor laser device, and has an n-GaAs substrate 88 and an n-G substrate as shown in FIGS.
A pair of multilayer film reflecting mirrors 90 provided on the aAs substrate 88.
A light emitting layer 94 having an active layer 92 is sandwiched between A and B and a pair of multilayer film reflecting mirrors 90A and 90B, and p provided on the multilayer film reflecting mirror 90B via a contact layer 96.
And a side electrode 98. As shown in FIG. 3B, the p-side electrode 98 is a ring-shaped electrode having a circular window 100 that transmits an optical signal, and is connected to the extraction electrode 102.

The n-side electrode of the second VCSEL 44 is the second
The PD 42 serves as a common electrode with the p-side electrode 82. Further, the common electrode 82 has a second VC as a lead electrode.
The insulating film 106 is formed between the contact plug 104 that penetrates the layer structure of the SEL 44 and is electrically connected to the common electrode 82.
It is provided through. By providing a lead wire to the contact plug 104, a current is drawn from between the p-side electrode (common electrode) 82 and the n-side electrode 84 of the second PD 42, and the p-side electrode 98 and the n-side electrode of the second VCSEL 44 are drawn. It is possible to easily inject a current between 82 (common electrode).

With the above configuration, the bidirectional optical communication system 30 of the present embodiment is a system capable of bidirectional optical communication through a single optical fiber 36, and the optical fiber 36 The configurations of the first and second optical signal transmission / reception devices 32 and 34 provided at both ends can be made compact and compact.

[0024]

According to the present invention, a long-wavelength surface-emitting light-emitting element and a short-wavelength light-receiving element optically coupled to the surface-emitting light-emitting element are provided on one of the transmitting and receiving sides. 1. An optical signal transmitting / receiving device of 1, and a light receiving element for long wavelength,
First and second optical signal transmitting / receiving devices by configuring a second optical signal transmitting / receiving device on the other transmitting / receiving side with a surface emitting type light emitting device for short wavelength, which is optically coupled on the light receiving device. And an optical communication system capable of performing two-way optical communication with the first and second optical signal transmission / reception devices via a single optical fiber. .

[Brief description of drawings]

FIG. 1 is a schematic diagram illustrating a configuration of an optical communication system according to an exemplary embodiment.

FIG. 2A and FIG. 2B are a cross-sectional view and a plan view showing a configuration of a first optical signal transmitting / receiving apparatus, respectively.

FIG. 3A and FIG. 3B are a cross-sectional view and a plan view showing a configuration of a second optical signal transmitting / receiving apparatus, respectively.

FIG. 4 is a diagram illustrating the concept of an optical communication system.

FIG. 5 is a schematic diagram showing a configuration of a conventional bidirectional optical communication system.

[Explanation of symbols]

10 ... Conventional bidirectional optical communication system, 12 ... Optical signal transmitting / receiving apparatus provided on one side, 14 ... Optical signal transmitting / receiving apparatus provided on other side, 16 ... Optical fiber,
18 ... 1st optical signal transmitter, 20 ... 1st optical signal receiver, 22 ... 2nd optical signal receiver, 24 ... 2nd optical signal transmitter, 30 ... Example of embodiment Optical communication system, 32 ... First optical signal transmitting / receiving device, 34 ... Second
Optical signal transmitter / receiver, 36 ... Optical fiber, 38 ... First VCSEL, 40 ... First PD, 42 ... Second PD, 44 ... Second VCSEL, 46 ... n-GaA
Substrate, 48 ... Multilayer mirror, 50 ... Active layer, 52
...... Emitting layer, 54 ...... Contact layer, 56 ...... Common electrode, 58 ...... n side electrode, 60 ...... Window, 62 ...... n-Ga
As substrate, 64 ... i active layer, 66 ... light receiving layer, 6
8 ... p-side electrode, 70 ... window, 72 ... contact plug, 74 ... insulating film, 76 ... n-InP substrate, 78 ...
... i active layer, 80 ... InGaAs light receiving layer, 82
...... Common electrode, 84 ...... n side electrode, 86 ...... Window, 88 ...
... n-GaAs substrate, 90 ... multilayer mirror, 92 ...
Active layer, 94 ... Light emitting layer, 96 ... Contact layer, 98
... p-side electrode, 100 ... window, 102 ... extraction electrode, 104 ... contact plug, 106 ... insulating film.

Claims (2)

[Claims] 1. An optical fiber having a single core between the first and second optical signal transmission / reception devices, which is provided with first and second optical signal transmission / reception devices on one transmission / reception side and the other transmission / reception side, respectively. An optical communication system for performing bidirectional optical communication via a first optical signal transmitting / receiving device, wherein a first surface emitting light emitting element for emitting an optical signal of a first wavelength and an absorption edge wavelength A first surface-emitting type light-emitting device which is composed of a compound semiconductor layer shorter than the first wavelength, is provided on the first surface-emitting type light-emitting device by optical coupling, and is optically coupled to one end of the optical fiber. A first light receiving element for transmitting an optical signal emitted from the element to enter the optical fiber and for receiving an optical signal having a second wavelength shorter than the absorption edge wavelength through the optical fiber; The optical signal transmitting / receiving device includes a second light receiving element that receives an optical signal of the first wavelength. And a compound semiconductor layer having an absorption edge wavelength shorter than the first wavelength, provided optically coupled to the second light receiving element, and optically coupled to the other end of the optical fiber. A second surface-emitting light-emitting element that transmits the optical signal of the first wavelength received via the second optical path to reach the light receiving element and emits the optical signal of the second wavelength via the optical fiber. A two-way optical communication system characterized in that 2. The first and second optical signal transmission / reception devices are each configured as a module in which a surface emitting light emitting element and a light receiving element are integrally optically coupled. Bidirectional optical communication system described.