JPH06204593A - Optical amplifier and semiconductor laser device - Google Patents

Abstract

PURPOSE:To obtain a rare earth-doped fiber optical amplifier having high reliability in low power consumption and a semiconductor laser device, from which a high fiber optical output is acquired in low bias. CONSTITUTION:The constitution of an optical amplifier is shown. A multiple wavelength light source 1 simultaneously emits the wavelengths of 1.47mum, 1.48mum and 1.49mum while being multiplexed. The wavelength synthetic excitation light 16 is projected to an Er-doped fiber (EDFA) 12, and the doped fiber is excited. Signal light having a 1.55mum wavelength is projected to the EDFA 12 under the state, thus outputting amplified light 14 through a wavelength filter 15. Each wavelength used at that time can excites EDFA with high efficiency even in any wavelength.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber amplifier device which is indispensable for realizing ultra-long-distance / ultra-multi-distribution optical fiber communication and a semiconductor laser device constituting the optical fiber amplifier device.

[0002]

2. Description of the Related Art In recent years, an optical amplification technique using an optical fiber doped with a rare earth element such as Er has rapidly progressed, and ultra-long-distance unrepeatered optical transmission and ultra-multi-distribution optical transmission are being realized. Here, as shown in FIG. 4, a pumping semiconductor laser 11 having a wavelength of 1.48 μm is used.
Is injected into an Er-doped optical fiber (hereinafter referred to as EDFA) 12 to be excited and then a signal light 13 having a wavelength of 1.55 μm
The signal light 14 thus amplified can be emitted by entering the signal light into the EDFA 12. Here, in order to obtain a high amplification factor, it is necessary to bring the EDFA into a highly excited state, and for that purpose, a very high output semiconductor laser for excitation is required. It is generally said that it is desirable to have an optical output of 100 mW or more.

FIG. 5 shows a typical fiber light output-bias current characteristic of a 1.48 μm semiconductor laser using an InGaAsP / InP material which has been used as a conventional pumping light source.
6 to obtain optical fiber output of 100 mW or more
A large current of 00 mA or more is required. However, FIG.
As is apparent from the graph, in the semiconductor laser, the luminous efficiency thereof is remarkably lowered due to the increase of the bias current and the heat generation of the active layer and the increase of the leak current. Further, injecting such a large current into one semiconductor laser resonator shortens the life of the device and it is difficult to obtain high reliability.

On the other hand, there is a method of using two pumping lasers to reduce the laser load. FIG. 6 shows an example of this method. Here, the lights emitted from the pumping lasers 11 and 11 'are combined by the polarization beam splitter 17 via the polarization maintaining fibers 18 and 18', respectively, and the EDFA 12 is generated.
Is incident on. Here, polarization-maintaining fibers 18, 1
The light emitted from 8'can be combined by making TE and TM incident on the deflecting beam splitter, respectively.

In this method, each laser can obtain a combined output of 100 mW with an optical output of about 60 mW, and the bias current of each laser can be reduced. However, even in this case, the bias current to each laser is about 400 mA, which is still insufficient from the standpoint of light emission efficiency and reliability. It is necessary to use more lasers, but in polarization combining, two or more lights are used. It cannot be synthesized.

[0006]

As described above, according to the conventional method, in order to obtain an optical fiber amplifier having a sufficient amplification factor, a large current is required for one pumping semiconductor laser and a large power consumption is caused by a decrease in luminous efficiency. In addition, there is a problem in that the life of the semiconductor laser is shortened by a large bias load and an optical amplifier with high reliability cannot be obtained. Further, even when a plurality of pumping light sources are used to reduce the load on the laser, the conventional polarization combining method has a problem in that the number of two pumps is limited and has not been greatly improved.

Therefore, an object of the present invention is to provide a rare earth-doped fiber optical amplifier having low power consumption and high reliability, and a semiconductor laser device which can obtain a high fiber optical output with a low bias.

[0008]

In order to solve the above-mentioned problems, the present invention integrates a plurality of single-wavelength oscillation lasers having different oscillation wavelengths within the excitation wavelength range of a rare earth-doped optical fiber in an array form. Semiconductor element and rare-earth-doped optical fiber, and a function of condensing and coupling each light emitted from the array-shaped semiconductor element to the rare-earth-doped optical fiber and a function of inputting and outputting a signal light having a wavelength having amplification sensitivity to the rare-earth optical fiber. An optical amplifying device characterized in that each resonator emits laser light of a single oscillation wavelength different from each other on the same semiconductor substrate, and the angle between the optical axis of each resonator and the emission end face is different. A semiconductor laser device having a plurality of resonators integrated therein.

[0009]

With the above-mentioned means, each pump laser can be driven with a low bias current, so that a high luminous efficiency can be obtained and an optical fiber amplifier device with low power consumption and high reliability can be obtained. It is possible to obtain a semiconductor laser device which can be well coupled to a fiber.

[0010]

EXAMPLES Examples of the present invention will be described below.

FIG. 1 shows the configuration of an optical amplifier as an embodiment of the present invention. Here, 1 is a multi-wavelength light source, and in the present embodiment, wavelengths 1.47 μm, 1.48 μm,
The wavelengths of 1.49 μm are simultaneously emitted and combined. The wavelength-combined pumping light 16 is incident on the Er-doped fiber (EDFA) 12 to pump the doped fiber. In this state, the signal light 13 having a wavelength of 1.55 μm is ED
Upon entering the FA 12, the amplified light 14 is output through the wavelength filter 15. Each wavelength used here can excite the EDFA with high efficiency at any wavelength.

Next, FIG. 2 shows an example of the multi-wavelength light source in detail. The multi-wavelength integrated laser array 2 is composed of three resonator stripes (3, 3 ′, 3 ″). Each resonator constitutes a distributed feedback laser including a diffraction grating having a different equivalent period, λ ₁ = 1.49 μm, λ ₂ = 1.48 μ
Light having a single oscillation wavelength of m, λ ₃ = 1.47 μm is radiated from the respective output ends (4, 4 ′, 4 ″). The respective output lights are collimated by the collimator lens 5 and are incident on the diffraction grating 6. Here, the respective (θ ₁ , θ ₂ , θ ₃ ) formed by the resonator stripes (3, 3 ′, 3 ″) and the emission end faces (4, 4 ′, 4 ″) of the integrated laser array are different. By
On the same spot on the diffraction grating 6, different incident angles (α ₁ ,
It can be incident at α ₂ , α ₃ ).

The first-order diffraction angle β has the following relationship with the incident angle α. α = sin ⁻¹ (λ / Λ−sin β) where Λ is the pitch of the diffraction grating. In this embodiment, in order to set Λ = 1.4 μm and β = 70 °, α ₁ = 7.16 for λ ₁ = 1.49 μm as the incident angle α.
Α ₂ = 6.74 ° for λ, λ ₂ = 1.48 μm, λ
_{For 3} = 1.47 μm, α ₃ = 6.33 °. Further, the distance between the diffraction grating 6 and the multi-wavelength integrated laser array is L ₁ 2.8 cm, the array interval is 200 μm, the angles θ ₁ = 89.82 ° and θ ₂ = 90.
By setting 00 ° and θ ₃ = 90.18 °, it is possible to obtain combined light having the same diffraction angle. At this time, the light of each wavelength can obtain a value of 80% or more as the diffraction efficiency. This diffracted light can be efficiently coupled to the optical fiber 8 through the condenser lens 7. As described above, in the present invention, the multi-wavelength synthetic light source can be formed with a simple structure by setting the angles of the optical axis of each resonator and the emission end face to be different from each other.

FIG. 3 shows the fiber light output of the combined light with respect to the total bias current to the array in FIG. It can be seen that compared with the case of the conventional example shown in FIG. 5, the total current is about 400 mA, the light output can be 100 mW or more, the light output saturation is small, and the high light output shows high luminous efficiency. This is because the laser of each wavelength operates at a low bias current of about 133 mA. As a result, it is possible to obtain a highly reliable semiconductor laser and optical amplifier in which the life of the element is not shortened by the conventional high bias current.

In the present embodiment, an integrated light source of three wavelengths is described, but the number of multiplexes and wavelength intervals are not limited to this as long as it is within the excitation wavelength of the EDFA. Further, the multi-wavelength integrated laser array of the present invention can be favorably used not only as an optical amplifier but also as a light source for wavelength division multiplexing transmission.

[0016]

As described above, the present invention provides a semiconductor element and a rare earth-doped optical fiber in which a plurality of single wavelength oscillation lasers having different oscillation wavelengths within the excitation wavelength range of the rare earth-doped optical fiber are integrated in an array, and An optical amplifying device having a function of condensing and coupling each light emitted from an array-shaped semiconductor element to the rare earth-doped optical fiber and a function of inputting and outputting a signal light having a wavelength having amplification sensitivity to the rare earth optical fiber. Since each pump laser can be driven with a low bias current, a high luminous efficiency can be obtained, and an optical fiber amplifier device with low power consumption and high reliability can be obtained.

Further, according to the present invention, a plurality of resonators which emit different oscillation wavelengths in the respective resonators on the same semiconductor substrate and have different angles between the optical axis of the respective resonators and the emission end face are integrated. The semiconductor laser device is characterized in that it is possible to obtain a semiconductor laser device capable of efficiently coupling laser light of a plurality of wavelengths to a fiber with a simple configuration, and its practical value is great.

[Brief description of drawings]

FIG. 1 is a block diagram of an optical amplifier of the present invention.

FIG. 2 is a configuration diagram of a semiconductor laser device of the present invention.

FIG. 3 is a light output-current characteristic diagram of the excitation light source of the present invention.

FIG. 4 is a configuration diagram of a conventional optical amplifier.

FIG. 5: Optical output-current characteristic diagram of conventional pumping light source

FIG. 6 is a configuration diagram of an optical amplifier having a conventional configuration.

[Explanation of symbols]

 1 Multi-wavelength light source 2 Multi-wavelength integrated laser array 3 Resonator stripe 4 Emitting facet 5 Collimating lens 6 Diffraction grating 7 Condensing lens 8 Single-mode fiber 11 Pumping semiconductor laser 12 Er-doped fiber amplifier (EDFA) 13 Signal light 14 Amplification light

Claims (3)

[Claims] 1. A semiconductor element in which a plurality of single-wavelength oscillation lasers having different oscillation wavelengths within an excitation wavelength range of a rare earth-doped optical fiber are integrated in an array, a rare earth-doped optical fiber, and the arrayed semiconductor element. An optical amplifying device comprising means for condensing / combining each emitted light from the optical fiber to the rare earth-doped optical fiber, and means for inputting / outputting signal light of a wavelength having an amplification sensitivity to the rare earth optical fiber. 2. An array-shaped semiconductor laser that emits light having a plurality of different oscillation wavelengths at desired angles and intervals, and a collimator lens, a plane diffraction grating, and a condenser lens are arranged in this order between the optical fibers. The emission angles and emission beam intervals from the arrayed lasers and the oscillation wavelengths are set so that the collimated beams of the respective wavelengths are incident on the same spot with respect to the planar diffraction grating and the diffraction angles of the respective wavelengths are as close to each other as possible. The optical amplifier according to claim 1, wherein the diffraction grating pitch is set. 3. A plurality of resonators emitting different single-oscillation wavelength laser beams from the respective resonators on the same semiconductor substrate and having different angles between the optical axis of each of the resonators and the emission end face. A semiconductor laser device characterized in that