JPS5878489A - Multiplex wavelength optical amplifier - Google Patents

Abstract

PURPOSE:To obtain the amplifier, which can directly amplify a light singal without photoelectric transducing action, can implement the amplification action by using one common element with respect to multiplex wavelength signal light, and has a compact, simple constitution. CONSTITUTION:Two facing reflecting surfaces 3 and 4 are providing in a single current injecting type semiconductor laser amplifier element 1. Light is inputted to one side and outputted from to other side. The reflecting surfaces 3 and 4 act as a half mirror. When a forward direction current is injected from a terminal 2, the element 1 starts laser oscillation at a certain current value or more. Under the bias state lower than this oscillation limit, the Fabry-P erot resonating type linear optical amplifier having a gain vs. frequency characterisic shown by a solid line is obtained. In this amplifier, each carrier wavelength of the incident multiplex wavelength signal light (f1...fN in frequency indication) is set so that it agrees with the frequency of a resonating point. When the multiplex wavelength signal light, whose carrier frequency is the frequency f1... or fN which is equal to the resonance frequency of the amplifier, is inputted into the resonating type optical amplifier 1, respective light is directly amplified, transmitted through the other reflecting surface 4, and taken out.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical amplifier suitable for optical communication systems using wavelength-multiplexed optical signals. In particular, it relates to an optical amplifier that directly increases wavelength-multiplexed optical signals without converting them into electrical signals.

Conventionally, an amplifier for relaying wavelength-multiplexed optical signals has a wavelength of 0.
Signal light whose wavelength has been multiplied by a JI4tk carrier wave is split into l light beams by a demultiplexer, and each light beam is amplified by a separate element. 41, in practical terms, the light is detected once, converted to an electrical signal, then identified and regenerated, and a laser oscillator is used again to generate a nine-light signal, after which the N-O beam is combined. It is composed of This rounding structure becomes complicated), and the scale of the repeater increases as the number of multi-order violets increases.

A method has also been considered in which the optical beam is branched into N beams and directly amplified by one unified amplifier for each beam without performing photoelectric conversion, but in this case as well, it is necessary to use a split #IL device and an optical amplifier in the equipment. ,
This requires a multiplexer, which complicates the IR structure, and the noise inevitably generated from each optical amplifier is sent out to the transmission line through the multiplexer, which degrades the signal-to-tone ratio of the transmission system. The shortcoming is that the relay interval is short and a practical design cannot be obtained.

The present invention is an amplifier that can amplify a direct 1ifK optical signal without performing opto-electrical conversion, and is capable of performing an amplification effect on wavelength-multiplexed signal light using one common element. It is an object of the present invention to provide a φ-type amplifier with a simple configuration.

The present invention is arranged so that the reflected light travels through the same optical path repeatedly, and is provided at the interface between 92 or more reflective surfaces and the outer reflective surface, and energy is supplied from the outside. The gain frequency width is set to be larger than the longitudinal mode frequency interval between the reflecting surfaces, and the R length of the carrier wave of the incident wavelength multiplexed signal light is equal to the resonant wavelength of this amplifier. ZtL-IPK-4L, and the wavelength width of each incident light is set to be p smaller than the wavelength width with the amplification gain measured by the resonant mode K of this amplifier. explain in detail.

FIG. 1 is a basic structural diagram of an apparatus according to an embodiment of the present invention. ! is a single current injection type semiconductor laser amplification element, and a bias current is injected from terminal 2. This element 1 has two opposing reflective surfaces 3.4, and light enters from one and exits from the other, as indicated by the arrows. Reflective surface 3.4F
Acts as a half mirror.

When a current is injected in the layer direction from the terminal 2 to the current injection type semiconductor laser amplification element lFi, laser laser oscillation starts when the current value exceeds a certain value. In the case of a low bias-like vagina (this oscillation limit), a 7-application Vero-resonant 1110 optical direct chain amplifier has a gain versus frequency characteristic as shown by the solid line in Fig. 2(a).

In FIG. 91(a), the horizontal axis shows frequency and the vertical axis shows gain. Figure K
A resonance point appears at every frequency # indicated by tp (in this example, about 110 G blood, about 27X length). This frequency fp is determined by the period of the longitudinal mode in which light travels back and forth between the reflection surfaces 3 and 40.

When the peaks of the resonance points are connected, the broken line in Figure 2 (,) is
Each has a small frequency width. □ In the frequency distribution shown by this broken line, if we consider the frequency interval f between the two points where the gain is the maximum and the gain is -, in this example, it is approximately 40,000Hsi or more (
1001 or less).

Also, considering the gain half width f for one resonance point, it is about 2 T-5 GHz. Maximum gain G is 20~
50 dB can be obtained. .

Such characteristics Ot! 4 of the wavelength multiplexed signal light that is transmitted to the width transmitter! ! -Carrier wavelength (fl, fl in frequency display)
, ...fl) are set to match the frequency of this resonance point. In the above example, the gain half width f,
is 4000 GII, and the resonance pitch fp is 1108H.
If (2), nearly 40 resonance points are obtained in the half-width fW of the gain, so the multiplexing number r remains up to about 4.0.

In other words, the frequency fl that matches the ★ line frequency of the amplifier
When wavelength-multiplexed signal light with carrier frequency , fl , ----f is input to the optical amplifier IK of the resonant layer, it becomes distorted.
The light is directly amplified and transmitted through another reflective surface 4 and extracted. The input frequencies f1, fl, ... -fM do not necessarily have to be next to each other, but they may be discrete. In this way, a single amplifier can input frequencies f1, fl, ...
,..."" Because all the multiplexed signal light of fN is directly amplified, the noise generated by the amplifier and blocked by the transmission path is 1. compared to the method of amplifying it with individual O amplification lIK.
//Ig, which makes it difficult to expand the relay interval.

The amplification gain is saturated as the input signal optical power increases, but when the gain decreases due to saturation, the saturated output is -10 to -sai in a normal semiconductor laser amplifier.
The value is s-'. In the present invention, which multiplexes and amplifies signals of one frequency, the amplifier output allowed for light of each frequency is 1/I of the above-mentioned saturation output value. For optical repeaters, this is not a major drawback.

Amplifier elements that can be used to implement the present invention include:
In addition to this, a similar wavelength multiplexing optical amplifier can be constructed by operating various lasers such as gas, solid, and dye lasers that perform axial mode oscillation above the threshold below the threshold and using them as amplifier elements.

As a further embodiment of the present invention, as a resonator for constructing a resonant type amplification element using a semiconductor gain medium or other medium other than the Fabry-Perot type, a five-piece resonator or an F14 resonator as shown in FIG. 3 or 4 is used. A ring resonator with two reflective surfaces (10 or 11) can be used. In this example as well, a biased medium is placed between each reflecting surface (XOt9#1ll).

Mayu, Figure 5 shows an input waveguide 12 and an output waveguide 1401 having an IK amplification gain, and a round shape with a length L to couple the waveguides 12 and 14. It is now possible to arrange the directional coupling waveguide 13 and use nine configurations. In this case, the Ka resonance frequency interval is Δν='/n, where n is the refractive index and C is the speed of light. The amplification center frequency is Δν N (N is an integer).

As described above, by using one resonant optical amplifier whose gain width is larger than the resonant frequency interval, it is possible to simultaneously amplify multiplexed signal light having a large number of frequencies that match the resonant frequency. In particular, if this is done with a semiconductor laser amplifier that is a small, high-gain, low-Q resonator, a high-performance optical repeater for wavelength multiplexing transmission can be easily constructed.

[Brief explanation of the drawing]

115th i! 1 is a basic structural diagram of an apparatus according to an embodiment of the present invention. FIG. 2 is a characteristic diagram and a frequency allocation diagram for explaining the operating principle. 3 and 4 are structural diagrams of another embodiment of the device of the present invention. Figure 5 is an explanatory diagram of an application example that operates based on the same principle. 1--Amplification medium (semiconductor laser element), 2--Bias current supply terminal, 3.4--Reflection surface. M 1 Zutsuta 2 Kenryo 3 Zutsuki 41￥l Kou 5 mouth

Claims (2)

[Claims] (1) Comprising two or more reflecting surfaces arranged so that the nine reflected lights repeatedly pass through the same optical path, and an amplification medium provided between the reflecting surfaces and supplied with external energy,
In a resonant optical amplifier, the gain frequency width is set to be larger than the longitudinal mode frequency interval determined by the interval between the reflecting surfaces, and is configured to amplify and extract incident light incident on an amplification medium. , the incident light is wavelength-multiplexed signal light, the wavelengths of the plurality of carrier waves of the wavelength-multiplexed signal light match any of the amplification lB8 resonance wavelengths, and the wavelength width of each incident light is within the resonant mode of this amplifier. A wavelength multiplexing optical amplifier characterized in that the amplification gain is set to be smaller than a certain wavelength width. (2) The wavelength multiplexing optical amplifier according to claim (1), wherein the number of reflecting surfaces is two, and the amplification medium is a semiconductor laser device to which a bias current lower than the oscillation limit is applied.