JPH1010371A - Optical transmitter-receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical transmitter-receiver capable of reducing crosstalk of lights between a transmission and a receiving and also capable of a monolithic constitution and capable of attaining a cost reduction and a high volume productivity. SOLUTION: In an optical transmitter-receiver provided with a light emitting element 1 converting an electric signal into an optical signal, a photodetector 2 converting an optical signal into an electric signal, a transmitting means transmitting the optical transmitting signal outputted from the light emitting element 1 via an optical fiber 7 and a receiving means inputting the optical receiving signal received via the optical fiber 7 to the photodetector 2, the transmitting means is provided with a first optical amplifier 10 having the amplification band made to correspond to the wavelength of the optical transmitting signal and amplifies the optical transmitting signal outputted from the light emitting element 1 to transmit it via the optical fiber 7 and the receiving means is provided with a second optical amplifier 11 having the amplification band made to correspond to the wavelength of the optical receiving signal and amplifies the optical receiving signal received via the optical fiber 7 to input it to the photodetector 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transceiver (module) having a light-emitting element and a light-receiving element used for bidirectional optical communication using one optical fiber.

[0002]

2. Description of the Related Art In recent years, the need for an optical communication system for performing bidirectional optical communication with one optical fiber has been increasing. To realize a bidirectional optical communication system, an optical transmitter and a receiver are indispensable. However, if these optical transmitters and receivers are individually configured, a transmitting / receiving device becomes large and a practical system cannot be realized. As a module having integrated transmission and reception functions, for example, a wavelength multiplexing transmission and reception module described in Japanese Patent Application Laid-Open No. 4-309908 is known. This module will be used for future optical subscriber networks such as PON (Passi
on Optical Network (ONU)
optical Network Unit) or optical LAN
Used for etc.

FIG. 12 shows a configuration of a conventional wavelength multiplexing transmission / reception module. 12, 100 is a light emitting element, 200 is a light receiving element, 300 and 400 are optical waveguides,
Reference numeral 500 denotes an optical WDM coupler, 600 denotes a wavelength multiplexing transmission / reception module (hereinafter simply referred to as a module), 700 denotes an optical fiber, 800 denotes a driving circuit, and 900 denotes a receiving circuit.

The operation will be described below. Light emitting device 100
The light having the wavelength λ1 which is a transmission signal output from the optical fiber 700 is transmitted to the optical fiber 700 via the optical waveguide 300 and the optical WDM coupler 500. On the other hand, the reception signal of wavelength λ2 that has entered the module 600 from the optical fiber 700 is received by the light receiving element 200 through the optical waveguide 400 via the optical WDM coupler 500. By performing wavelength division multiplexing (WDM) for transmission and reception, two-way simultaneous communication is enabled.

[0005]

By the way, in the configuration shown in FIG. 12, the transmission signal of the wavelength λ1 is transmitted by the optical waveguide 300,
There is a problem of so-called light crosstalk, which is received as stray light by the light receiving element 200 in the same module 600 via the optical WDM coupler 500, the optical waveguide 400, or directly from the light emitting element 100.

Generally, the light output from a light emitting element is larger by 20 to 40 dB than the light receiving power in a light receiving element. Therefore, depending on the configuration of the module, transmission and reception cannot be performed due to optical crosstalk.

Further, from the viewpoint of cost and mass productivity, the optical transmitting and receiving module desirably employs a system in which not only optical passive elements such as optical couplers and optical waveguides but also optical active elements such as light emitting and receiving elements are monolithically formed on a substrate. It is. However, it has been difficult to realize a practical monolithic optical transmission / reception module due to the above-mentioned problem of optical crosstalk.

Therefore, the present invention can reduce optical crosstalk by increasing optical isolation between transmission and reception by using an optical amplifier having a wavelength characteristic. As a result, a monolithic configuration can be realized, and cost reduction and mass production can be achieved. It is an object of the present invention to provide an optical transmission / reception device capable of achieving high performance.

[0009]

An optical transmitting and receiving apparatus according to the present invention comprises a light emitting element for converting an electric signal to an optical signal, a light receiving element for converting an optical signal to an electric signal, and multiplexing and demultiplexing a plurality of optical signals. An optical multiplexer / demultiplexer, transmitting means for transmitting an optical transmission signal output from the light emitting element to an optical fiber via the optical multiplexer / demultiplexer, and receiving the optical transmission signal from the optical fiber via the optical multiplexer / demultiplexer. A receiving unit for inputting an optical reception signal to the light receiving element, wherein the transmitting unit includes a first optical amplifier having an amplification band corresponding to a wavelength of the optical transmission signal; The optical transmission signal output from the element is amplified by the first optical amplifier and sent out to the optical fiber via the optical multiplexer / demultiplexer, and the receiving means includes:
A second having an amplification band corresponding to the wavelength of the optical reception signal;
A light receiving signal received from the optical fiber via the optical multiplexer / demultiplexer is amplified by the second optical amplifier and input to the light receiving element. The reflected component of the output from the optical multiplexer / demultiplexer (optical coupler) is attenuated by the second optical amplifier having the wavelength selection characteristic disposed in front of the light receiving element, so that light isolation between transmission and reception is increased. .

Also, in the optical transmitting and receiving apparatus of the present invention, the light emitting element, the light receiving element, the transmitting means (including the first optical amplifier) and the receiving means (including the second optical amplifier) are on the same substrate. Since the device is monolithically integrated, cost reduction and mass productivity can be achieved.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 schematically shows the configuration of an optical transceiver (hereinafter simply referred to as a module) according to a first embodiment of the present invention. , Light receiving element 2, first optical amplifier (semiconductor optical amplifier) 10, second optical amplifier
(Optical semiconductor amplifier) 11, optical coupler (optical multiplexer / demultiplexer) 5, and transmission / reception circuit 12.

An optical transmission signal output from the light emitting element 1 propagates through the optical waveguide C1 and enters the first optical amplifier 10, and an optical transmission signal output from the first optical amplifier 10 propagates through the optical waveguide C2. Then, the signal is input to one terminal of the optical coupler 5. The optical coupler 5 and the optical fiber 7 are optically connected via an optical waveguide C5.

When an optical signal, for example, wavelength-multiplexed, transmitted through the optical fiber 7 propagates through the optical waveguide C5 and is input to the optical coupler 5, the optical reception signal is demultiplexed to obtain an optical signal.
From the other terminal is guided to the optical waveguide C3. The optical transmission signal propagating through the optical waveguide C2 and input to the optical coupler 5 propagates through the optical waveguide C5.

An optical reception signal propagating through the optical waveguide C5 is input to the second optical amplifier 11, and an optical transmission signal output from the second optical amplifier 11 propagates through the optical waveguide C4 and is received by the light receiving element 2. Is done.

The light emitting element 1 is driven by the transmission / reception circuit 12 to convert the electric signal S1 into an optical transmission signal. Light receiving element 2
Converts the optical reception signal propagating through the optical waveguide C4 into an electric signal S2 and sends it to the transmission / reception circuit 12. That is, the transmission / reception circuit 12 includes a transmission circuit to the light emitting element 1 and the light receiving element 2
Are integrated with each other.

The wavelength λ1 (eg, 1.55) which is a transmission signal output from the light emitting element 1 (eg, a laser diode)
μm) propagates through the optical waveguide C1 and is amplified by the first optical amplifier (semiconductor optical amplifier) 10. Further, the light propagates through the optical waveguide C2 and is input to the other terminal of the optical coupler 5. It is sent to the optical fiber 7 via C5.

The optical coupler 5 and the optical fiber 7 are connected to an optical waveguide C5.
Are optically connected via a. The optical reception signal having the wavelength λ2 (for example, 1.3 μm) input from the optical fiber 7 propagates through the optical waveguide C5 and is input to the optical coupler 5, and propagates through the optical waveguide C3 from the other terminal of the optical coupler 5 to be transmitted through the optical waveguide C3. The light is amplified by the second optical amplifier (semiconductor optical amplifier) 11, further propagated through the optical waveguide C4, and received by the light receiving element 2 (for example, a photodiode).

The light emitting element 1 is driven by the transmission / reception circuit 12 to convert the electric signal S1 into an optical transmission signal. Light receiving element 2
Converts the optical reception signal transmitted through the optical waveguide C4 into an electric signal S2 and transmits the electric signal S2 to the transmission / reception circuit 12.

FIG. 2 shows first and second optical amplifiers 10 and 11.
3 shows an example of the wavelength characteristic of FIG. The first and second optical amplifiers (semiconductor optical amplifiers) 10 and 11 are configured to change the band gap by changing the component compositions, respectively. As shown in FIG. Having an amplification band G1 centered on the wavelength λl of the received signal;
The second optical amplifier 11 has a wavelength characteristic having an amplification band G2 centered on the wavelength λ2 of the optical transmission signal.

In FIG. 7, in the wavelength characteristic of the first optical amplifier 10, the gain is set to 10 dB in the amplification band G1 and λ
2 is -10 dB. That is, the optical signal having the wavelength of the optical transmission signal is amplified, while the optical signal having the wavelength of the optical reception signal is attenuated.

In the wavelength characteristic of the second optical amplifier 11, the gain is 10 dB in the amplification band G2 and -10 dB at λ1. That is, the optical signal having the wavelength of the optical transmission / reception signal is amplified, but the optical signal having the wavelength of the optical transmission signal is attenuated.

Next, with respect to the optical transmitting / receiving module having the configuration shown in FIG. 1, i) the light having the wavelength λ1 (optical transmitting signal), which is the transmission signal output from the light emitting element 1, is transmitted through the optical waveguide C1 and the first optical amplifier. 10, the optical waveguide C2, the optical coupler 5, the optical waveguide C3, the second optical amplifier 11, and the light received by the light receiving element 2 via the optical waveguide C4. Receiving signal) from the optical fiber 7, the optical waveguide C5, the optical coupler 5, the optical waveguide C3, the second
Of the signal level until the light is received by the light receiving element 2 via the optical amplifier 11 and the optical waveguide 4.

For example, it is estimated that the light transmission output of the light emitting element 1 at the wavelength λ1 is 0 dBm, the isolation between the λ1 and λ2 of the optical coupler 5 is 30 dB, and the optical reception signal power at the wavelength λ2 of the optical fiber 7 is -30 dB. To

Based on these numerical values, the observation points (points A to C) on each of the optical waveguides C1 to C4 until the optical transmission signal of wavelength λ1 and the optical reception signal of wavelength λ2 are received by the light receiving element 2.
FIG. 3 shows the result of calculating the signal level at point (D).

In FIG. 3, the signal level of the optical transmission signal at the point A in FIG. 1 is "0 dBm", and the signal level at the point B is amplified by the first optical amplifier 10 by 10 dB from the wavelength characteristic shown in FIG. , The signal level at point C is attenuated by 30 dB by passing through the optical coupler 5 to “−20 dBm”, and the signal level at point D is
According to the waveform characteristics shown in FIG.
It is attenuated to “−30 dBm”.

On the other hand, the signal level of the optical reception signal at the point C in FIG. 1 is “−30 dBm”, and the signal level at the point D is 10 second according to the wavelength characteristic shown in FIG.
The signal is amplified by dB to become "-20 dBm".

Similarly, FIG. 4 shows the case of an optical transmission / reception module (see FIG. 12) according to the prior art. In FIG.
i) The wavelength λ1 which is the transmission signal output from the light emitting element 1
Of the optical waveguide 300, the optical coupler 500, and the optical waveguide 40
0, until it is received by the light receiving element 200, and ii).
The figure shows a state in which light having a wavelength λ2, which is a received signal, enters from the optical fiber 700 and is received by the light receiving element 200 via the optical coupler 500 and the optical waveguide 400.

In FIG. 4, similarly to FIG. 3, for example, the wavelength and the optical output of the light emitting element 1 are λ1, +10 dBm, the optical coupler 5
Is 30 dB, the wavelength in the optical fiber 7 and the optical reception signal power are λ2 and −30 dBm.

Based on this numerical value, the observation points (points A and D) on the optical waveguides 300 and 400 until the optical transmission signal of wavelength λ1 and the optical reception signal of wavelength λ2 are received by the light receiving element 200. FIG. 4 shows the result of determining the signal level of ()).

In FIG. 4, the signal level of the optical transmission signal at point A in FIG. 12 is "0 dBm", and the signal level at point D is "-30 dBm".

On the other hand, the signal level of the optical reception signal at point D in FIG. 12 is "-30 dBm". As is clear from FIG. 3, in the case of the optical transceiver module of the present invention, the signal level of the optical transmission signal received by the light receiving element 2 is “−30”.
dBm ", the signal level of the optical reception signal received by the light receiving element 2 is" -20 dBm ", and the signal level of the optical transmission signal of wavelength λ1 leaked into the optical waveguide C3 is higher than the signal level of the optical reception signal. "10 dB" smaller.

On the other hand, as is apparent from FIG. 4, in the case of the conventional optical transmitting and receiving module, the signal level of the optical transmission signal received by the light receiving element 200 is “−20 dBm”, and the optical reception signal received by the light receiving element 200 is Signal level is "-30
In dBm, the signal level of the optical transmission signal leaked into the optical waveguide 400 is “10” higher than the signal level of the optical reception signal.
dB "is large.

To reduce the light crosstalk, the signal level of the light transmission signal received by the light receiving element 2 (i in FIG. 3)
It is necessary that the signal level of the optical transmission signal at the point D) is attenuated more than the signal level of the optical reception signal (ii in FIG. 3).

In the conventional case (see FIG. 4), the signal level of the optical transmission signal of the optical reception signal at the point D is higher by 10 dBm, and in the case of the present invention (see FIG. 3), the optical transmission signal of the optical reception signal at the point D is higher. Is 10 dBm smaller. That is, according to the present invention, as compared with the conventional case, the signal level of the optical transmission signal received by the receiving element 2 is set to “20d
Bm "can be attenuated.

As described above, the wavelength λ is output by the second optical amplifier 11.
2, the optical isolation between transmission and reception (20 dB in the numerical example) can be increased by attenuating the optical transmission signal of wavelength λ1 leaked into the optical waveguide C3 of FIG.

For the received signal, since the second optical amplifier 11 operates as an optical preamplifier, if the shot noise limit is achieved by the low-noise second optical amplifier 11, the receiving sensitivity is improved as compared with the prior art.

Further, by providing the first optical amplifier 10, as is apparent from FIGS. 3 and 4, the optical output of the light emitting element 1 (signal level at point A of the optical transmission signal) can be reduced by 10 dB from the conventional one. The received light power (signal level at point D of the received light signal) in the light receiving element 2 can be increased by 10 dB as compared with the related art. Therefore, the level difference between light emission and light reception is reduced by about 20 dB as compared with the related art, and there is an advantage that the transmitting circuit to the light emitting element 1 and the receiving circuit of the light receiving element 2 can be easily integrated or brought close to each other.

By the way, a laser diode having a low threshold can obtain an output of about 100 μW at a relatively small applied current, for example, 1 mA. Therefore, if a low-threshold laser diode is used for the light emitting element 1, the current applied to the laser can be further reduced, and the manufacture of the integrated transmission / reception IC becomes easier.

The internal configuration of the transmission / reception circuit (transmission / reception integrated IC) 12 includes a driving circuit for the light emitting element 1 and an APC (Au).
front-end amplifier for ATC (Atomically Power Control) circuit and photo detector
automatic gain control circuit, filter, timing extraction circuit and semiconductor optical amplifier (first,
All or some of the bias circuits and the like for the second optical transceivers 10 and 11) are included.

AG to the first and second optical amplifiers 10 and 11
It is conceivable that a C circuit is built in to perform AGC not only at the electric level but also at the optical level. If you do this,
The reception level and the dynamic range of the APC are dramatically increased.

Since it is relatively difficult to form a capacitor component having a large value inside the IC, it is common to externally provide a filter for signal equalization or timing extraction. Further, if echo cancellation is performed at the electric level inside the IC, isolation between transmission and reception can be further enhanced.

The integrated IC can have either a hybrid or monolithic configuration, but a monolithic is desirable from the viewpoint of cost and mass productivity. As shown in FIG. 5, the overall configuration of the optical transmitting / receiving module shown in FIG. 1 is a PLC (Pl) in which optical passive elements such as an optical coupler 5 and an optical waveguide are formed on a substrate.
light emitting and receiving elements 1, 2, 1st, and 2nd on passive lightwave circuit (anner Lightwave Circuit).
A configuration in which the second optical amplifier (semiconductor optical amplifier) and the transmission / reception circuit 12 are arranged is possible.

With this configuration, the yield is expected to be relatively low and the yield is improved. A low-loss silica glass fiber is suitable for the optical fiber 7. The light emitting element 1 has an inexpensive FP (Fa
(bry-Perot) type laser diode can be used. Also, if a spot size conversion type laser is used, coupling loss between the laser output and the optical waveguide and stray light can be reduced,
Better transmission / reception characteristics can be obtained. However, the optical fiber 7
It is also possible to use a plastic fiber which is inexpensive and easy to handle. In this case, the light wavelength used is 0.8μ
m, and an inexpensive Si-based photodiode can be used for the light receiving element.

In the PLC, it is effective to use a waveguide type optical amplifier doped with a rare earth element instead of the semiconductor optical amplifier. This uses quartz or multi-component glass as the host glass material,
A glass waveguide to which a rare earth element such as r or Pr is added is formed by a flame deposition method, an ion exchange method, or the like. The rare-earth-element-doped waveguide is excited by a high-power laser to operate as an optical amplifier. In general, a rare earth-doped optical amplifier has a higher gain and output than a semiconductor optical amplifier, so that higher isolation can be obtained.

Further, an optical element having wavelength selectivity can be applied instead of the optical coupler 5. At present, a dielectric multilayer filter having higher isolation than an optical coupler made by PLC is dug and buried in the substrate, or a diffraction grating is formed on the substrate to guide a desired signal to a desired optical waveguide. Configuration.

As a further inexpensive module configuration, PI
C (Photonic Integrated Cir
cut) can be considered. This is not only the optical passive element such as the optical coupler 5 and the optical waveguide, but also the light emitting and receiving elements 1, 2, the first,
In this method, active elements such as second optical amplifiers (semiconductor optical amplifiers) 10 and 11 and a transmission / reception circuit (integrated transmission / reception IC) 12 are formed on a substrate (InP). According to this method, alignment of each element is not required, which is suitable for mass productivity and cost reduction.

First and second optical amplifiers (semiconductor optical amplifiers)
If some of the four devices 10, 10, light emitting element 1 and light receiving element 2 are integrated, a cheaper module can be obtained. For example, if the light emitting element 1 and the first optical amplifier (semiconductor optical amplifier) 10 and the light receiving element 2 and the second optical amplifier (semiconductor optical amplifier) 11 are integrated, respectively, The optical waveguides between the elements 1 and 2 can be omitted, and there are advantages such as lower cost.

In addition, the light emitting element 1, the light receiving element 2, and the first
The same effect can be obtained even if the optical amplifier (semiconductor optical amplifier) 10 and the second optical amplifier (semiconductor optical amplifier) 11 are integrated. The light emitting element 1 has a DFB (Distributed Feed) that does not require reflection at the end face because of the configuration of a PIC.
Back) lasers are suitable.

Further, between the transmission and reception lines, that is, the light emitting element 1
-First optical amplifier 10-Optical waveguide C2 and light receiving element 2-
If the light absorption layer 13 as shown in FIG. 1 is provided between the second optical amplifier 11 and the optical waveguide C3, stray light that does not pass through the optical coupler 5 can be further cut.

Although the WDM coupler is suitable for the optical coupler 5, the reflection between the respective optical elements is sufficiently suppressed, and the first and second optical couplers are used.
If the isolation between transmission and reception by the optical amplifiers 10 and 11 is large, a directional coupler type optical coupler can also be applied.

Incidentally, the optical connection between the optical coupler 5 and the optical fiber 7 particularly tends to cause light reflection. When a semiconductor optical amplifier is used without an optical isolator, a problem of oscillation arises, so that measures against light reflection are particularly important.

A measure against light reflection to solve this problem will be described with reference to FIG. FIG. 5 shows the main components of the components for preventing light reflection of the optical transceiver module 6 shown in FIG. The same parts as those in FIG. 1 are denoted by the same reference numerals.

In FIG. 5, the optical coupler 5 is a Mach-Zehnder type WDM coupler, but may be a directional coupler type or another type. The measures against light reflection shown in FIG. 5 are shown below.

A) Optical transmitting / receiving module (for example, PI
C) The AR (A) is connected to an end face (hereinafter sometimes referred to as a PIC end face) 30 of the connection side of the optical waveguide C5 and the optical fiber 7 of 6).
antiReflection) coat (anti-reflection film) 1
Apply 6.

B) A so-called window structure in which the optical waveguide C5 is cut in the middle without extending to the PIC end face 30. c) Glass rod 1 between optical waveguide C5 and optical fiber 7
Insert 5

An optical connector ferrule 17 is attached to a connection end of the optical fiber 7 with the optical transmission / reception module 6, and a physical connection (PC: Physical Co.) between the core 7 a constituting the center of the optical fiber 7 and the glass rod 15.
ntact) is possible.

The glass rod 15 functions as a lens with respect to the optical waveguide C5, receives an optical signal propagated and radiated in the optical waveguide C5, and focuses the optical signal on the core 7a of the optical fiber 7. ing.

The principle of light reflection reduction will be briefly described. Light radiated from the optical waveguide 19 having the window structure to the glass rod 15 having the lens structure is condensed on the core 7a of the optical fiber 7 contacted with the PC and transmitted through the optical fiber. With the PC contact, a light reflection attenuation of, for example, 40 dB or more can be obtained.

Even if light reflection occurs at the optical connector ferrule 17 or the glass rod 15, the AR coating 30 is applied to the PIC end face 30, and since the optical waveguide C5 has a window structure, the ratio at which the reflected light 35 is coupled to the optical waveguide C5. Is small. That is, even if the optical signal 36 radiated from the optical waveguide C5 to the glass rod 15 is reflected by the optical connector ferrule 17 or the glass rod 15, the reflected light 35 is reflected by the optical waveguide C5.
The end face of the optical waveguide C5 is PIC so as not to enter
It is arranged apart from the end face 30 (window structure).

It is to be noted that some of these light reflection countermeasures can be used in combination or used alone. At this time, a matching oil can be used. Further, if the optical fiber is fixed using the split sleeve 18, a connector with a guide, or a V-groove, an improvement in positional accuracy can be expected. (Second Embodiment) FIG. 6 shows a configuration of an optical transceiver module according to a second embodiment of the present invention.
The same parts as those in FIG. 1 are denoted by the same reference numerals, and only different parts will be described. That is, the first optical amplifier (semiconductor optical amplifier) 10 in FIG. 1 is omitted, and the light emitting element 1 is directly connected to the optical coupler 5 via the optical waveguide C6.

FIG. 7 shows the result of observation at the same observation points (points A, C and D) with the signal levels of the optical transmission and reception signals in this case being the same as in FIG. In FIG. 7, the optical transmission signal output from the light emitting element 1 needs "+10 dBm" because the first optical amplifier 10 is omitted, and therefore the signal level of the optical transmission signal at point A in FIG. "1
0 dBm ". Since the first optical amplifier 10 is omitted, the signal level of the optical transmission signal at the point C is attenuated by 30 dB by passing through the optical coupler 5 as it is.
20 dBm ”, and the signal level at point D is
The optical amplifier 11 is attenuated by 10 dBm from the waveform characteristics shown in FIG.

On the other hand, the signal level of the optical reception signal at the point C in FIG. 6 is “−30 dBm”, and the signal level at the point D is equal to 10 degrees according to the wavelength characteristic shown in FIG.
The signal is amplified by dB to become "-20 dBm".

In this case, the attenuation of the signal level of the optical transmission signal received by the receiving element 2 is the same as in the first embodiment, but the level difference between the transmission and reception (the signal level of the optical transmission signal at point A and the optical The difference between the received signal and the signal level at point D) is larger than in the first embodiment.

However, a module can be manufactured with a simpler configuration. Further, the optical reception signal of wavelength λ2 is
1 longer than the optical transmission signal (for example, λ2 = 1.3)
μm, λ1 = 1.55 μm), the light receiving element 2
Since it originally has a characteristic of a low-pass filter, the light receiving element itself cannot have wavelength selectivity by blocking the band gap at λ1.

Even in such a case, since the second optical amplifier (semiconductor optical amplifier) 11 has the wavelength characteristic as shown in FIG. 2, good optical isolation can be obtained. That is, the configuration shown in FIG. 6 is effective both when the wavelength of the optical transmission signal is shorter and longer than the wavelength of the optical reception signal. (Third Embodiment) FIG. 8 shows the configuration of an optical transceiver module according to a third embodiment of the present invention.
The same parts as those in FIG. 1 are denoted by the same reference numerals, and only different parts will be described. That is, the second optical amplifier (semiconductor optical amplifier) 11 of FIG. 1 is omitted, and the optical coupler 5 and the light receiving element 2 are directly connected by the optical waveguide C7.

FIG. 8 shows the result of observation at the same observation points (points A, B, and D) with the signal levels of the optical transmission and reception signals in this case being the same as in FIG. 9, the signal level of the optical transmission signal at the point A is “0 dBm”, and the signal level at the point B is amplified by the first optical amplifier 10 by 10 dBm from the wavelength characteristic shown in FIG.
Since the optical amplifier 11 is omitted, it is attenuated by 30 dBm by passing through the optical coupler 5 as it is, and the signal level at the point D becomes “−20 dBm”.

On the other hand, the optical reception signal is transmitted to the second optical amplifier 11.
Is omitted, the signal level at point D is
“−30 dBm”. In this case, the attenuation of the signal level of the optical transmission signal received by the receiving element 2 is smaller than that in the first embodiment, but as in the case of the first embodiment, the transmission / reception level difference (optical transmission signal Between the signal level at point A and the signal level at point D of the received optical signal.
And the module can be manufactured with a simpler configuration.

Regarding the isolation of light between transmission and reception, if the optical reception signal of wavelength λ2 is selected to be shorter in wavelength than the optical transmission signal of wavelength λ1, the light receiving element 1 itself can have wavelength selectivity. That is, the configuration shown in FIG. 8 is effective only when the wavelength of the optical transmission signal is longer than the wavelength of the optical reception signal.

Since the semiconductor optical amplifier and the light-emitting element have similar compositions and structures, if they oscillate well, they have the advantage that they can be more easily integrated than the combination of the semiconductor optical amplifier and the light-receiving element. (Fourth Embodiment) FIG. 10 shows the configuration of an optical transceiver module according to a fourth embodiment of the present invention.
The same parts as those in FIG. 8 are denoted by the same reference numerals, and only different parts will be described. That is, the optical waveguide C of FIG.
7, an optical filter 14 is inserted.

In this case, the effects such as the attenuation of the signal level of the optical transmission signal received by the receiving element 2 and the level difference between the transmission and reception are the same as those of the third embodiment. The insertion effectively acts on light isolation between transmission and reception. That is, even if the optical reception signal having the wavelength λ2 is selected to have a longer wavelength than the optical transmission signal having the wavelength λ1, the optical filter 14 has wavelength selectivity, so that good characteristics can be obtained.

Similarly, contrary to the case of FIG. 10, a second optical amplifier (semiconductor optical amplifier) 11 is arranged on the receiving side, and the first optical amplifier (semiconductor optical amplifier) 10 on the transmitting side is optically connected. A configuration in which the filter 14 is replaced is also possible, and has the same effect as the present embodiment. (Fifth Embodiment) FIG. 11 shows the configuration of an optical transceiver module according to a fifth embodiment of the present invention.
The same parts as those in FIG. 1 are denoted by the same reference numerals, and only different parts will be described. That is, the optical transceiver module 6 shown in FIG. 11 does not include the transceiver circuit 12. A circuit corresponding to the transmission / reception circuit 12 includes, as external circuits of the optical transmission / reception module 6, for example, a drive circuit 8 connected to the light emitting element 1 and a reception circuit 9 connected to the light receiving element 2.

When the optical passive elements and the electric elements constituting the drive circuit 8 and the receiving circuit 9 cannot be integrated on the same substrate, as shown in FIG. 11, an optical transmitting / receiving module configured by integrating only the optical passive elements is used. 6 is also possible.

As described above, according to the present invention,
The reflection component of the light output from the light emitting element 1 is attenuated by the second optical amplifier 11 having a wavelength characteristic disposed in front of the light receiving element 2, so that light isolation between transmission and reception is increased.

Further, by amplifying the optical output from the light emitting element 1 by the first optical amplifier 10 disposed in front of the light emitting element 1, the level difference between the emitted light and the received light can be suppressed as compared with the prior art. Transmitting circuit to light emitting element 1 and light receiving element 2
There is an advantage that the receiving circuits can be easily integrated or brought close to each other.

If the optical amplifier is also monolithically built in the optical transceiver module, an economical optical transceiver module can be easily manufactured. Further, FIGS. 1, 6, and 8
And the like are integrated on the same substrate and housed in one package, and an antireflection film (AR coating) is provided on the end face of the package that is optically connected to the optical fiber 7.
By forming a window structure in which the optical waveguide 16 is formed and the end face of the optical waveguide C5 that guides the optical transmission signal to the optical fiber 7 is separated from the end face 30 of the package provided with the antireflection film 16, light reflection measures can be taken. .

[0076]

As described above, according to the optical transmitting / receiving apparatus of the present invention, an optical amplifier having wavelength characteristics is used.
Optical isolation between transmission and reception can be increased to reduce optical crosstalk. As a result, a monolithic configuration is possible, and cost reduction and mass productivity can be achieved. That is, by using an optical amplifier having wavelength characteristics, the isolation of light between transmission and reception is increased, and the level difference between transmission and reception can be reduced, so that good transmission and reception characteristics can be obtained. This allows P
IC configuration becomes possible, thereby reducing costs and improving the reliability of the module.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an optical transceiver module according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an example of wavelength characteristics of first and second optical amplifiers (semiconductor optical amplifiers).

FIG. 3 is a view showing each observation point on each of the optical waveguides C1 to C4 until an optical transmission signal of wavelength λ1 and an optical reception signal of wavelength λ2 of the optical transmission and reception module having the configuration shown in FIG. The figure which showed an example of the signal level observed in (A point-D point).

FIG. 4 shows observation points (points A to D) on each of the optical waveguides C1 to C4 until an optical transmission signal of wavelength λ1 and an optical reception signal of wavelength λ2 of the conventional optical transceiver module are received by the light receiving element. FIG. 3 is a diagram showing an example of a signal level observed in FIG.

FIG. 5 is a view for explaining specific means of light reflection measures.

FIG. 6 is a diagram showing a configuration of an optical transceiver module according to a second embodiment of the present invention.

FIG. 7 shows observations on the optical waveguides C6, C3, and C4 until the optical transmission signal of the wavelength λ1 and the optical reception signal of the wavelength λ2 of the optical transceiver module having the configuration shown in FIG. The figure which showed an example of the signal level observed at the point (point A, point C, point D).

FIG. 8 is a diagram showing a configuration of an optical transceiver module according to a third embodiment of the present invention.

FIG. 9 is a view illustrating each of optical waveguides C1, C2, and C7 until an optical transmission signal of wavelength λ1 and an optical reception signal of wavelength λ2 of the optical transceiver module having the configuration shown in FIG. The figure which showed an example of the signal level observed at the point (point A, point B, point D).

FIG. 10 is a diagram showing a configuration of an optical transceiver module according to a fourth embodiment of the present invention.

FIG. 11 is a diagram showing a configuration of an optical transceiver module according to a fifth embodiment of the present invention.

FIG. 12 is a diagram showing a configuration example of a conventional optical transceiver module.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Light emitting element, 2 ... Light receiving element, 5 ... Optical coupler (optical multiplexer / demultiplexer), 6 ... Optical transmitting / receiving module, 7 ... Optical fiber, 8 ...
Driving (transmitting) circuit, 9 receiving circuit, 10 first optical amplifier, 11 second optical amplifier, 12 transmitting / receiving circuit (integrated transmitting / receiving IC), 13 light absorbing layer, 14 optical filter, 1
5: glass rod, 16: AR coating, 17: optical connector ferrule, 18: split sleeve, C1 to C7: optical waveguide.

Claims (5)

[Claims] A light emitting element for converting an electric signal to an optical signal; a light receiving element for converting an optical signal to an electric signal; an optical multiplexer / demultiplexer for multiplexing and demultiplexing a plurality of optical signals; Transmitting means for transmitting the transmitted optical transmission signal to the optical fiber via the optical multiplexer / demultiplexer, and receiving means for inputting an optical reception signal received from the optical fiber via the optical multiplexer / demultiplexer to the light receiving element An optical transmitting and receiving apparatus comprising: a first optical amplifier having an amplification band corresponding to a wavelength of the optical transmission signal, wherein the transmitting unit transmits the optical transmission signal output from the light emitting element to the first optical amplifier. Amplifying by the optical amplifier and sending out to the optical fiber via the optical multiplexer / demultiplexer; the receiving means includes a second optical amplifier having an amplification band corresponding to a wavelength of the optical reception signal; Optical multiplexer / demultiplexer from fiber Optical transceiver and wherein the input to the light receiving element of the optical signal received is amplified by the second optical amplifier through. 2. A light emitting element for converting an electric signal into an optical signal, a light receiving element for converting an optical signal into an electric signal, a transmitting means for transmitting an optical transmission signal output from the light emitting element via an optical fiber, An optical transmission / reception device comprising: a reception unit that inputs an optical reception signal received via the optical fiber to the light receiving element; wherein the transmission unit has an amplification band corresponding to a wavelength of the optical transmission signal. An optical transmission / reception device, comprising: amplifying an optical transmission signal output from the light emitting element by the optical amplifier and transmitting the amplified signal to the optical fiber via the optical multiplexer / demultiplexer. 3. A light emitting element for converting an electric signal into an optical signal, a light receiving element for converting an optical signal into an electric signal, an optical multiplexer / demultiplexer for multiplexing and demultiplexing a plurality of optical signals, and an output from the light emitting element. Transmitting means for transmitting the obtained optical transmission signal to the optical fiber via the optical multiplexer / demultiplexer, and receiving means for inputting the optical reception signal received from the optical fiber via the optical multiplexer / demultiplexer to the light receiving element In the optical transmitting and receiving apparatus, the receiving means includes an optical amplifier having an amplification band corresponding to the wavelength of the optical reception signal, and receives the optical signal received from the optical fiber via the optical multiplexer / demultiplexer. An optical transmitting and receiving apparatus, wherein a signal is amplified by the optical amplifier and input to the light receiving element. 4. The optical transceiver according to claim 1, wherein the light emitting element, the light receiving element, the transmitting unit, and the receiving unit are integrated on a same substrate. . 5. The light emitting element and the light receiving element, and the transmitting means and the receiving means are integrated on the same substrate, housed in one package, and provided on an end face of the package optically connected to the optical fiber. An anti-reflection film is formed, and an end face of the optical waveguide for guiding the optical transmission signal to the optical fiber is disposed apart from an end face of the package provided with the anti-reflection film. 3
The optical transceiver according to any one of the above.