JP2001188140A - Photoelectric integrated circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric integrated circuit for receiving a local oscillation optical signal 122 and an intermediate frequency optical signal 123 whose wavelengths are different and which are transmitted through an optical fiber, separating both signals, effectively performing frequency mixing and generating a high output electric RF signal. SOLUTION: This integrated circuit is constituted so that a means 102 for separating a local oscillation optical signal 122 and a intermediate frequency optical signal 123, a first conversion means 105 for inputting the local oscillation optical signal 122 and outputting an local oscillation electric signal 122, a second conversion means 106 for inputting the intermediate frequency optical signal 123 and outputting an intermediate frequency electric signal 123 and a mixing means 107 outputting a mixture signal of the local oscillation electric signal and the intermediate frequency electric signal are monolithically integrated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an opto-electric integrated circuit, and more particularly to an opto-electric integrated circuit for frequency mixing used in fiber wireless communication using an optical fiber link.

[0002]

2. Description of the Related Art In a situation where mobile communication or wireless communication such as wireless LAN is rapidly developing, fiber wireless communication using an optical fiber link is expected to develop. In particular, the millimeter-wave fiber wireless communication using the millimeter-wave band frequency is expected to be a future wireless communication because it is easy to effectively use frequency resources and increase the bit rate of transfer data.

In wireless communication, a mixer for mixing an IF signal processed by an LO signal and data and extracting the mixed signal as an RF signal is indispensable. In conventional optical fiber wireless communication using optical fibers, a control station generates an LO signal and an IF signal, mixes the LO signal and an IF signal that has been signal-processed with data, and uses the resulting RF signal to operate an optical modulator. In general, a configuration in which an optical subcarrier on which a data signal is superimposed by driving is generated.

[0004] Such a configuration requires an electric frequency mixer, an amplifier, and an optical modulator. Since these devices are more expensive as the frequency becomes higher, there is a problem in realizing millimeter-wave fiber wireless communication.

As a method for solving this problem, there has been proposed a configuration in which an optical LO signal and an optical IF signal are transmitted through an optical fiber and an electric RF signal is generated in an antenna station. The optical LO signal can be generated by using, for example, a semiconductor mode-locked laser, and since the frequency of the IF signal is extremely low compared to the frequency of the RF signal frequency, it is not difficult to generate an optical IF signal processed by data. . In a configuration in which an optical LO signal and an optical IF signal are transmitted through a fiber and an electric RF signal is generated in the antenna station, the antenna station generates an electric RF signal from the optical LO signal and the optical IF signal.
A photoelectric mixer that generates a signal is one of the most important devices.

As a method of realizing a function of generating an electric RF signal from an optical LO signal and an optical IF signal, a photoelectric frequency mixer utilizing the nonlinearity of the operation of a photodiode has been proposed (M. Tsuchiya and
T. Hosida, IEEE Transacti
ons on Microwave Theoryan
dTechniques, Volume 47, p. 1
342, 1999).

FIG. 3 shows how a photodiode is used as a photoelectric frequency mixer. The optical LO signal 322 and the optical IF signal 323 are fiber-transmitted as optical signals having different wavelengths. The two are multiplexed by the optical coupler 324, transmitted through one optical fiber, and input to the photodiode 301. Photodiodes have a non-linear effect that the output is saturated when the light input increases. This by the nonlinear effect, is optical IF signal is mixed with the optical LO signal frequency f _IF with a frequency f _LO, RF signals of frequency f _LO ± f _IF is taken out from the photodiode.

However, since it is difficult to provide a large nonlinearity without deteriorating the high speed inherent in the photodiode, the photoelectric mixer using the photodiode is an RF mixer.
Low conversion efficiency to signal. Also, since the photodiode has no amplifying action, this method uses a large output RF.
It is also difficult to get a signal. Therefore, practically RF
Since a signal amplifier is required, an increase in cost cannot be avoided. The increase in cost is significant because the higher the frequency, the more expensive the amplifier.

In a configuration in which an optical LO signal and an optical IF signal are transmitted through a fiber to generate an electric RF signal in an antenna station, the optical LO signal and the optical IF signal are transmitted through separate fibers, and each of the antenna stations transmits an electric LO signal.
A configuration is also possible in which the signal is converted into a signal and an electric IF signal, and the electric signal of both is frequency-mixed to generate an RF signal. However, this configuration not only requires a double fiber, but also requires at least a pair of OE converters and an electric frequency mixer at each antenna station,
The cost of the system is inevitable.

[0010]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in the prior art, and transmits a local oscillation signal and an intermediate frequency signal as optical signals having different wavelengths through one optical fiber. It is another object of the present invention to provide an opto-electric integrated circuit for frequency mixing that enables an antenna station to extract an RF output with a high conversion efficiency and a large output.

[0011]

According to the present invention, there is provided an opto-electric integrated circuit comprising: means for separating a local light signal and an intermediate frequency optical signal; and a first means for inputting the local light signal and outputting a local electric signal. Monolithically integrated means for converting, a second converting means for inputting the intermediate frequency optical signal and outputting an intermediate frequency electric signal, and a mixing means for outputting a mixing signal of the local electric signal and the intermediate frequency electric signal. It is characterized by having done.

According to another aspect of the present invention, there is provided an opto-electric integrated circuit comprising: means for separating a local light signal and an intermediate frequency optical signal; converting means for inputting the local light signal and outputting a local electric signal; Conversion means for inputting the generated electric signal and the intermediate frequency optical signal and outputting a mixed signal of the intermediate frequency electric signal and the local electric signal is monolithically integrated.

Here, it is preferable to use an arrayed waveguide grating as a means for separating.

Further, it is preferable to use one of a photodiode and a phototransistor as the first conversion means or the second conversion means.

Further, when a photodiode and a phototransistor are present as active elements in such a monolithic integrated circuit, the photodiode is formed by using a base layer, a collector layer and a collector contact layer of the phototransistor. The crystal structure and manufacturing process for monolithic integration can be simplified.

Further, it is preferable to monolithically integrate an antenna which emits a mixing signal into space as a radio wave.

[0017]

(First Embodiment) FIG. 1 shows a first embodiment of an opto-electric integrated circuit for photoelectric mixing according to the present invention.

The optoelectronic integrated circuit 101 for photoelectric mixing according to the present invention has a semiconductor array waveguide grating 102 which is a means for separating a local light signal and an intermediate frequency optical signal, and receives the local light signal and inputs a local electric signal. , A photodiode 105 as a first converting means for outputting an intermediate frequency optical signal, and a photodiode 106 as a second converting means for outputting an intermediate frequency electric signal, a local electric signal and an intermediate frequency electric signal. The mixer circuit 107, which is a mixing means for outputting a mixing signal, is monolithically integrated.

The monolithic integration of the semiconductor array waveguide grating 102 and the semiconductor active element is performed, for example, by using “Pa”
caged Polarization-Insen
sitive WDM Monitor with L
ow Loss (7.3dB) and wide Tu
ning Range (4.5 nm) "(M. Khot
Oku, H .; Sanjoh, S .; Oku, Y .; Kado
ta and Y. Yoshikuni, IEEE P
photonics Technology Lette
rs, Vol. 10, p. 125, 1998).

In this embodiment, the mixer circuit 107
Are configured using a heterojunction phototransistor (constituted by a bipolar transistor) as an active semiconductor element. Photodiodes 105 and 106
Are manufactured using a contact layer of a heterojunction phototransistor by a process of manufacturing a heterojunction phototransistor. This technology is disclosed in Japanese Patent Application No.
No. 19460. Therefore, the crystal layer structure and fabrication process for fabricating the opto-electric integrated circuit of the present invention is sufficient if it is for fabricating a semiconductor array waveguide grating and a heterojunction phototransistor. In FIG. 1, the power supply and the bias circuit are omitted.

At the control station 121 of the fiber wireless communication, a local light signal (optical LO) having a frequency f _LO having a different wavelength is used.
Signal) 122 and the frequency f _IF processed by the data
The intermediate frequency optical signal (optical IF signal) 123 having the following is multiplexed by the optical coupler 124 and emitted through one optical fiber. By generating an optical LO signal using, for example, a mode-locked semiconductor laser diode, a modulator operating in the band of the LO signal is not required.

The antenna station 111 includes an opto-electrical integrated circuit for photoelectric mixing 101 and an antenna 112 for emitting an RF signal output from the photoelectric integrated circuit as a radio signal. The signal light of two wavelengths transmitted in the fiber is
Semiconductor array waveguide grating 1 in optoelectronic integrated circuit 101
02, the light is split into an optical LO signal 103 and an optical IF signal 104, and converted into electrical LO signals and IF signals by photodiodes 105 and 106, respectively.

The two signals are mixed by a mixer circuit 107 to generate an RF signal having a frequency of f _LO + f _IF or f _LO -f _IF , and emitted as a radio wave by an antenna 112. Note that, if necessary, an RF amplifier can be increased in strength by inserting an electric amplifier between the photodiode and the mixer circuit or after the mixer circuit. When an electric amplifier is inserted, if a heterojunction phototransistor is used as an active device constituting the same as in a mixer circuit, the number of manufacturing steps does not increase.

If the photoelectric integrated circuit of this embodiment is used,
The antenna station can emit a sufficiently large output RF wave from the optical LO signal and the optical IF signal transmitted by the light of two wavelengths, and the configuration of the antenna station is simplified, so that the It is possible to reduce the size and cost. Further, since it is not necessary to use an optical modulator for the LO signal band in the control station, the entire system can be configured at low cost.

(Second Embodiment) FIG. 2 shows a second embodiment of the optoelectronic integrated circuit for photoelectric mixing of the present invention. In an electric integrated circuit 201 for photoelectric mixing, a semiconductor array waveguide grating 202, a photodiode 205, a heterojunction phototransistor 206, and an antenna 207 are monolithically integrated on a semiconductor substrate. The photodiode 205 is, as in the first embodiment,
Since it is manufactured by the heterojunction phototransistor manufacturing process using the base layer, the collector layer, and the collector contact layer of the heterojunction phototransistor, the crystal structure and manufacturing for manufacturing the optoelectronic integrated circuit for photoelectric mixing are described. It is sufficient that the process is for fabricating a semiconductor array waveguide grating and a heterojunction phototransistor. In FIG. 2, a power supply and a bias circuit are omitted.

In the present embodiment, the configuration of the control station and the two-wavelength signal light
01 by the semiconductor array waveguide grating 202 in FIG.
_LO of the optical LO signal 203 and the frequency f _IF of the optical IF signal 204
The operation mode until the signal is demultiplexed is the same as that of the first embodiment. The split optical LO signal 203 is converted into an electrical LO signal by a photodiode 205,
Input to the base terminal of heterojunction phototransistor 206.

On the other hand, the optical IF signal is introduced into the heterojunction phototransistor 206, and electrons and electrons are transmitted in the light absorption region.
A hole pair is generated. Accordingly, the heterojunction phototransistor 206 to, ready to LO signal and the IF signal is input, the nonlinearity possessed by the transistor amplifying effect, and both are mixed, the frequency f _LO ± f _IF of R
An F signal is generated, guided to an antenna 207 monolithically integrated on the same semiconductor substrate, and emitted into space as a radio wave. If necessary, a frequency filter is inserted between the heterojunction phototransistor 206 and the antenna 207 so that the frequency f _LO + f _IF or f _LO −f _IF
Can be extracted. Also,
The photodiode 205 is replaced with a heterojunction phototransistor to increase the intensity of the LO signal input to the phototransistor operating as a frequency mixer, or to the antenna station while maintaining the intensity of the LO signal input to the phototransistor. It is possible to weaken the intensity of the introduced optical LO signal.

Further, the bias applied to the phototransistor replacing the photodiode 205 is adjusted,
LO signal and IF input to phototransistor 206
It is also possible to increase the frequency conversion efficiency by changing the signal intensity ratio.

When the opto-electrical integrated circuit for frequency mixing of the present invention is used, as in the case of the first embodiment, the antenna LO can sufficiently separate the optical LO signal and the optical IF signal transmitted by the two-wavelength light from the antenna station. It is possible to emit a high-output RF radio wave. Furthermore, in this embodiment, the configuration of the opto-electric integrated circuit for frequency mixing itself is simplified, and the antenna is also monolithically integrated, so that the antenna station can be constituted only by the integrated circuit of the present invention, and the antenna station can be reduced in size. And cost reduction.

Further, in the present embodiment, since a phototransistor having an amplifying action is used for an element for performing photoelectric conversion and photoelectric frequency mixing, the intensity of the optical LO signal and the optical IF signal is reduced, that is, the burden on the control station is reduced. Can be reduced.

[0031]

As described above, if the opto-electric integrated circuit for frequency mixing according to the present invention is used, a local light signal and an intermediate frequency light signal having different wavelengths transmitted through one fiber are received, and both signals are received. , And efficient frequency mixing can be performed to generate a high-output electric RF signal.

Further, the opto-electric integrated circuit for frequency mixing of the present invention in which the antenna is monolithically integrated can emit the RF signal generated by the mixing into space as a radio wave. In fiber wireless communication, these functions are the functions of the antenna station itself, and the integrated circuit of the present invention makes the configuration of the antenna station compact and simple, so that the antenna station can be installed at low cost.

Further, if an antenna station having such a function can be realized, in a fiber radio communication system, an electric mixer and an optical modulator are not required in a control station, so that the whole system can be significantly reduced in price. Become.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a first embodiment of a photoelectric mixing circuit for frequency mixing according to the present invention.

FIG. 2 is a conceptual diagram showing a second embodiment of the opto-electric integrated circuit for frequency mixing according to the present invention.

FIG. 3 is a conceptual diagram showing a conventional photoelectric frequency mixer using a photodiode.

[Explanation of symbols]

 101: opto-electric integrated circuit for photoelectric mixing of the present invention; 102: semiconductor array waveguide grating (separating means); 103: local light signal (optical LO signal); 104: intermediate frequency optical signal (optical IF signal); ... photodiode (conversion means), 106 ... photodiode (conversion means), 107 ... mixer circuit (mixing means), 111 ... antenna station, 112 ... antenna, 121 ... control station, 122 ... local light signal (optical LO signal) 123: Intermediate frequency optical signal (optical IF signal), 124: optical coupler, 201: opto-electric integrated circuit for photoelectric mixing of the present invention, 202: semiconductor array waveguide grating, 203: optical LO signal, 204: optical IF signal Reference numeral 205: Photodiode, 206: Heterojunction phototransistor, 207: Antenna, 211: Antenna Reference numeral 221: control station, 222: optical LO signal, 223: optical IF signal, 224: optical coupler, 301: photodiode, 302: antenna, 311: antenna station, 321: control station, 322: optical LO signal, 323 ... Optical IF signal, 324 ... Optical coupler.

Continuation of the front page (72) Inventor Kiyoto Takahata 2-3-1 Otemachi, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Yoshifumi Muramoto 2-3-1 Otemachi, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Seiji Fukushima 2-3-1 Otemachi, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Tetsuichiro Ohno 2-3-1, Otemachi, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Yoshiyuki Doi 2-3-1 Otemachi, Chiyoda-ku, Tokyo F-term (reference) 2H037 AA01 BA02 BA11 DA03 DA06 2H047 KA03 KA12 LA18 MA07 PA06 QA02 TA05 5F049 MA01 MA11 NB01 RA10 5K002 AA03 AA04 BA05 BA07 BA16 DA02 FA01

Claims (6)

[Claims] 1. A means for separating a local light signal and an intermediate frequency optical signal, first converting means for inputting the local light signal and outputting a local electric signal, and inputting the intermediate frequency optical signal. A second converting means for outputting an intermediate frequency electric signal,
An opto-electric integrated circuit, wherein mixing means for outputting a mixing signal of the local electric signal and the intermediate frequency electric signal is monolithically integrated. 2. A means for separating a local light signal and an intermediate frequency optical signal, a conversion means for inputting the local light signal and outputting a local electric signal, the local electric signal and the intermediate frequency optical signal. And a conversion means for outputting a mixed signal of the intermediate frequency electric signal and the local electric signal by monolithic integration. 3. The opto-electric integrated circuit according to claim 1, wherein said means for separating is an arrayed waveguide grating. 4. The optoelectronic integrated circuit according to claim 1, wherein said first or second conversion means is one of a photodiode and a phototransistor. 5. A photo-diode and a photo-transistor as the first or second conversion means, wherein the photo-diode comprises a base layer of the photo-transistor,
The optoelectronic integrated circuit according to claim 4, wherein the optoelectronic integrated circuit is formed using a collector layer and a collector contact layer. 6. The opto-electric integrated circuit according to claim 1, wherein an antenna for emitting the mixing signal into space as a radio wave is monolithically integrated.