JPH1154842A - Light source for optical integrated type optical communication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the system configuration of an optical communication system, to save space, and to enable turning it also into a light source for a wavelength multiple transmission by arranging and integrating semiconductor lasers, light modulators and semiconductor light amplifiers on a same substrate. SOLUTION: A light signal is output from a laser 1 comprising a semiconductor element, propagates through a waveguide layer 2, and is incident on a light modulator 3. Within the light modulator 3, the light signal is modulated by a modulation speed, depending upon an optical communication system. The modulated light signal further propagates through a waveguide layer 4, is amplified inside a light amplifier 5 consisting of a semiconductor element, and then is output to an optical fiber 7 via a light output port 6. At the rear of the semiconductor laser 1, a photodiode 9 for monitoring the output from the laser is arranged in the configuration for keeping the light output from the laser constant. These light function portions are arranged and integrated on a same substrate 8 in configuration.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light source for generating, modulating and amplifying an optical signal used for optical communication and the like.
In particular, the present invention relates to a light source for integrated optical communication used for high-speed and large-capacity optical communication.

[0002]

2. Description of the Related Art In recent years, with the increase in capacity of information communication, a high-speed and large-capacity optical communication transmission system using an optical fiber has been constructed. At present, transmission using optical communication is SDH
There is a need to construct a high-speed, large-capacity communication system of about 2.488 Gb / s, which is used in SONET, etc., and more than 10 Gb / s. Also, in some optical submarine cable networks connecting between continents, a wavelength division multiplexing transmission system is adopted, and it is important to construct a high-speed, large-capacity optical communication system. At present, in this optical communication transmission system, as a means for generating an optical signal, a method in which a semiconductor laser is used and electric modulation is performed directly on the semiconductor laser is mainly used.

[0003]

However, in direct modulation of a semiconductor laser, the modulation speed is limited,
In order to perform ultra-high-speed and large-capacity communication such as 10 Gb / s, it is necessary to develop a semiconductor laser capable of high-speed modulation. It is also the cause. Further, even in a configuration in which an optical modulator is arranged at a stage subsequent to a semiconductor laser, there is a problem that optical signal power is reduced due to optical loss of the optical modulator. In order to solve this problem, there is a means to compensate the loss using an optical fiber amplifier,
In this method, the system becomes complicated and the scale is increased due to an increase in power consumption and cost due to the use of the optical fiber amplifier. Further, there is a possibility that the optical signal waveform is deteriorated due to the influence of the nonlinear optical effect by the optical fiber amplifier.

[0004]

Means for Solving the Problems The present invention is for solving these problems, and includes a semiconductor laser, an optical modulator,
By adopting a configuration in which the semiconductor optical amplifiers are arranged and integrated on the same substrate, the system configuration of the optical communication system can be simplified and the space can be saved.
Further, by adopting a configuration in which a plurality of semiconductor lasers, optical modulators, semiconductor optical amplifiers, and optical multiplexers are integrated on the same substrate, a light source for wavelength division multiplexing transmission can be used.

[0005]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram for explaining an optical integrated type optical communication light source according to the present invention. An optical signal is output from a laser 1 composed of a semiconductor element, propagates through a waveguide layer 2 and enters an optical modulator 3. In the optical modulator 3, the optical signal is modulated at a modulation speed depending on the optical communication system.
The modulated optical signal further propagates through the waveguide layer 4, is amplified in the optical amplifier 5 composed of a semiconductor device, and is output to the optical fiber 7 via the optical output port 6. Behind the semiconductor laser 1, a photodiode 9 for monitoring the output from the laser is arranged to keep the optical output of the laser constant. These optical functional units are arranged and integrated on the same substrate 8. FIG. 3 shows an example of a light source used for conventional 10 Gb / s 4-wavelength multiplex transmission.

Optical signals λ1, λ2, λ3, λ4 having different wavelengths output from the respective semiconductor lasers are input to an optical fiber and input to an optical modulator. Each optical signal input to the optical modulator is 2.488. Modulated at Gb / s modulation frequency. The modulated optical signal is transmitted through an optical fiber, multiplexed by an optical multiplexer, and then input to an optical fiber amplifier to compensate for loss in the optical modulator and optical multiplexer. Is output. As the optical fiber amplifier, an optical amplifier using an optical fiber doped with erbium ions, which are rare earth elements, is usually used.

Since this optical amplifier uses optical components such as an excitation light source, an amplification optical fiber, an optical multiplexer, and an optical isolator, it has a relatively large configuration, and furthermore, the excitation light source used therein. Requires large power consumption. FIG. 2 is a diagram showing an integrated optical communication light source for 10 Gb / s four-wavelength multiplex transmission according to the present invention.

Semiconductor lasers 10, 11, 1 having different wavelengths
Optical signals λ1, λ2, λ output from
3, .lambda.4 propagates through the waveguide layer and the respective optical modulators 14, 1
The light is incident on 5, 16, and 17. 2.488 Gb /
Modulation is added at a modulation rate of s. The modulated optical signal further propagates through the waveguide layer, and the semiconductor optical amplifiers 18, 1
After being amplified by 9, 20, and 21, they are multiplexed by an optical multiplexer 22 and output to the outside via an output optical fiber 24 via an optical output port 23. The output optical signal has a wavelength multiplexed transmission capacity of 10 Gb / s. Each optical functional component is arranged on a substrate 25. Each semiconductor laser is
By providing the PIN photodiodes 26, 27, 28, and 29 and adding a function of monitoring the optical output from the semiconductor laser, a temporally stable optical output can be obtained.

Although the present invention has been described with respect to a light source integrated with four waves, it is necessary to integrate the number of signal light wavelengths according to the transmission capacity required in a communication system. As the semiconductor laser, a semiconductor laser that can oscillate stable continuous light may be used, but it is preferable to use a DFB laser or a DBR laser having a stable spectral characteristic and a narrow spectral line width because of high-speed modulation. Also, when the number of multiplexed wavelengths increases,
It is preferable to use an array type semiconductor laser device in which the semiconductor laser device has an array structure. Further, the wavelength of the optical signal output from each semiconductor laser usually needs to be a wavelength required in a communication system. Generally, the wavelength standardized by ITU-T is used.

Further, in the present invention, the configuration in which the modulated signal light is amplified and then combined is described. However, there is no problem if the modulated signal is combined and then amplified together. When the interval between each optical signal light wavelength is narrow,
When the number of multiplexed signal lights is small, it is desirable to amplify after multiplexing.

In the case of the light intensity modulation system, the light modulator
Although it is desirable to use a branching interference type optical modulator, other modulators may be used as long as similar effects can be obtained. Also,
As a modulation method, there is a phase modulation method. In this case,
It is necessary to use an optical phase modulator.

In addition, even if the substrate material on which the semiconductor laser is disposed and the substrate material on which the optical modulator and the semiconductor optical amplifier are disposed are different, they may have an integrated structure.
Further, it is desirable that these integrated components be arranged on a device such as a Peltier device that can maintain a constant temperature.

[0013]

As described above, according to the present invention, by arranging and integrating a semiconductor laser, an optical modulator, and a semiconductor optical amplifier on the same substrate, the system configuration of an optical communication system can be simplified, and furthermore, Space can be saved. Conventionally, a semiconductor laser device having strict modulation characteristics has been required. However, an inexpensive continuous-wave semiconductor laser can be used as the semiconductor laser used in the present invention. In addition, by integrating a plurality of semiconductor lasers, optical modulators, and semiconductor optical amplifiers, it is possible to use a light source for wavelength division multiplexing transmission. The present invention can be provided as a light source of an inexpensive high-speed and large-capacity transmission system that can obtain stable optical output characteristics without the influence of the nonlinear optical effect.

[Brief description of the drawings]

FIG. 1 is a diagram showing an optical integrated type optical communication light source according to an embodiment of the present invention.

FIG. 2 is a diagram showing an optical integrated light source for four-wavelength multiplex communication according to an embodiment of the present invention.

FIG. 3 is a diagram showing a conventional optical integrated light source for four-wavelength multiplex communication.

[Explanation of symbols]

 1, 10, 11, 12, 13, DFB semiconductor lasers 2, 4, waveguide layers 3, 14, 15, 16, 17, branch interference optical modulators 5, 18, 19, 20, 21, semiconductor optical amplifiers 6 , 23 Optical output port 7, 24 Optical fiber 8, 25 Substrate 9, 26, 27, 28, 29, PIN photodiode 22, Optical multiplexer

Claims (2)

[Claims] 1. An optical integrated communication light source comprising a semiconductor laser and an optical modulator, wherein a semiconductor optical amplifier is provided at a subsequent stage of the optical modulator to compensate for optical loss of the optical modulator using the semiconductor optical amplifier. Characterized in that a semiconductor laser, an optical modulator and a semiconductor optical amplifier are integrated on the same substrate. 2. A light source for integrated optical communication according to claim 1, wherein two or more semiconductor lasers, the same number of optical modulators as the semiconductor lasers, and semiconductor optical amplifiers are arranged for the purpose of wavelength multiplexing. An optical multiplexing unit for multiplexing optical signals, in which an optical signal emitted from each semiconductor laser passes through each optical modulator or a semiconductor optical amplifier and is then multiplexed. light source.