JPH11142901A - Optical transmission device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify an optical transmission device for removing the distortion of signal light arising in consequence of the refractive index dispersion of an optical fiber. SOLUTION: The signal light Os via the optical fiber F1 is in a distorted state with respect to a wavelength. An optical parametric amplifier element 10 executes amplification with injected pumping light Op and generates amplified light Osa amplifying the signal light Os and idler light Oi . The idler light Oi is the inversion of the waveform with respect to the wavelength of the signal light Os . The idler light Oi is selected by a filter 11 and is outputted via the optical fiber F2. As a result, the distortion that the signal light Os has in the optical fiber F1 is corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmission device for correcting refractive index dispersion and propagation loss of an optical fiber when performing optical communication using the optical fiber for long-distance communication.

[0002]

2. Description of the Related Art FIG. 2 is a configuration diagram of a conventional optical transmission device. When performing long-distance optical communication, signal light propagating through the optical fiber is distorted due to the refractive index dispersion of the optical fiber. This is because the frequency transmitted in the optical fiber is ω _s
This is a phenomenon that occurs because the long wavelength side frequency component ω _s1 of the signal light O _{s has} a high plate transfer speed and the short wavelength side component ω _s2 is slow. Therefore, in the conventional optical fiber transmission device,
Optical fibers F1 and F at equal distances
2, and a QPM-DFG (Quasi Phase Matching-
Difference Frequency Generation) 1.
The QPM-DFG 1 is frequency propagated through the optical fiber F1 receives the signal light O _s of omega _s, converted light O _c of the waveform with respect to the wavelength of the signal light O _s is inverted, the signal light O _s conversion and it has a function of generating by the incidence of the pump light O _p wavelength band different frequency omega _p is the light O _c. QPM
The output side of the -DFG1, O _s of the output of the QPM-DFG 1, O _c, of the O _p, a filter 2 which passes only the converted light O _c of omega _c whose frequency desired, the filter 2 is An optical amplifier (EDF) that amplifies the output converted light O _c
A) 3 is connected. By such a configuration, as shown in FIG. 2, the wavelength of the signal light O _s (frequency)
Optical signal waveform is obtained by amplifying the converted light O _c inverted relative to the transmission, because it is propagated to the optical fiber F1 and equidistant optical fiber F2, the refractive index signal light waveform distortion is corrected by balancing the destination Is done.

[0003]

However, the conventional optical transmission device has the following problems. QPM-D
In the optical transmission device using the FG1, difference frequency between the signal light O _s of the pump light O _p and frequency omega _s of the frequency ω _p ω _c (=
ω _p −ω _s ) is used as converted light. Since this difference frequency ω _c is weaker than the signal light O _{s, a} loss of optical loss (usually about −20 dB) always occurs when performing wavelength conversion.
On the other hand, when an optical signal propagates through the optical fibers F1 and F2, a transmission loss of about -0.1 dB / Km usually occurs, and a coupling loss is required to couple the QPM-DFG1 to the optical fiber F2. Occur. In order to correct these losses, an optical amplifier 3 is required. The provision of the optical amplifier 3 not only complicates the optical transmission device, but also
Efficiency becomes worse economically.

[0004]

In order to solve the above-mentioned problems, the present invention has the following configuration in an optical transmission device. That is, a first optical fiber and a second optical fiber that divide a communication section for performing optical communication into two equal parts, a signal light through the first optical fiber are input, and pump light is injected, and an optical parametric The amplification using the effect is performed, the amplified signal light is amplified with the intensity of the pump light, and the idler light is amplified with the intensity of the pump light while the waveform related to the wavelength is inverted with respect to the signal light and the amplified light. And a filter that selects only idler light output from the optical parametric amplifier and outputs the selected idler light to the second optical fiber. According to the present invention, since the optical transmission device is configured as described above, signal light is input to the optical parametric amplification element via the first optical fiber. The signal light input to the optical parametric amplifier is distorted with respect to wavelength by the first optical fiber. The optical parametric amplifier performs amplification with the injected pump light, and generates amplified light and idler light. The idler light is a light obtained by inverting the waveform related to the wavelength of the signal light, and the light whose distortion is inverted with respect to the signal light and which is amplified. Only the idler light selected by the filter is output via the second optical fiber. The idler light is distorted by the second optical fiber, whereby the distortion of the signal light received by the first optical fiber is corrected. Therefore, the above problem can be solved.

[0005]

FIG. 1 is a block diagram of an optical transmission device showing an embodiment of the present invention. This optical transmission device has two optical fibers F1 and F2 for long-distance transmission. These optical fibers F1 and F2 are laid at equal distances in a communication section as in the related art. Each optical fiber F
1 and F2 are each constituted by a single mode optical fiber having a wavelength of 1.55 μm, for example. Optical fiber F1
Is an optical parametric amplifier (OPA: Optical) formed of a nonlinear material such as a semiconductor AlGaAs.
Parametric Amplify Device) 10 is connected, and a filter 11 is provided on the output side of the optical parametric amplification element 10.
Is connected. The output side of the filter 11 is connected to the optical fiber F2. Optical parametric amplifier 1
0 amplifies by an optical parametric effect to generate an amplified light O _sa and an idler light O _i having a wavelength of λ ₂ , and the optical parametric amplifying element 10 receives the wavelength λ ₁ from the optical fiber F _1. together with the signal light O _s of 1.54μm is input, the pump light O _p of wavelength lambda ₃ becomes configured to be implanted. However, the optical parametric amplification element 10 is formed with a fine periodic structure (grating) in a medium so as to satisfy the following conditions so that amplification by the optical parametric effect can be performed.

[0006]

(Equation 1) However, omega _1; amplified light O _sa frequency omega _2; idler light O _i of the frequency omega _3; pumping light O _p of the frequency n _1; amplified light O _sa refractive index n _2; refractive index of the idler O _i n _3; refractive index E ₃ of the pump light O _p; pumping light O _p of the field strength d; second order nonlinear optical constant of the medium will now be described an operation of the optical transmission apparatus of FIG.

[0007] The signal light O _s is given to the optical parametric amplification element 10 via the optical fiber F1. However,
The frequency is ω as shown in a waveform 20 relating to the frequency shown in FIG.
₁ of the signal light O _s is while propagating through the optical fiber F1,
The optical fiber F1 is distorted like a waveform 21 by the refractive index dispersion. This is because the frequency transmitted in the optical fiber is ω _s
This is a phenomenon that occurs because the long wavelength side frequency component ω _s1 of the signal light O _{s has} a high plate transfer speed and the short wavelength side component ω _s2 is slow. Optical parametric amplification device 10 that inputs the distorted signal beam O _s (1) and if satisfy formula (2), the pump light O power in proportion to the square of the electric field intensity E ₃
with _p, to produce an amplified light O _sa and idler light O _i was amplified power of the signal light O _s exponentially. Moreover, the frequency satisfies the following equation (3). ω ₂ = ω ₃ −ω ₁ (3) Therefore, the distortion method regarding the frequency of the idler light O _i is as follows.
The distortion of the distorted signal light O _s (amplified light O _sa ) is positionally inverted (waveform 22 in FIG. 1). Filter 11
From a signal output of the optical parametric amplification device 10 to remove the component of the amplified light O _sa and the pump light O _p, idler O
Only _i is taken out and given to the optical fiber F2. Since the optical fiber F2 has the same length as the optical fiber F1, the destination via the optical fiber F2, the waveform of the distorted signal beam O _s in the optical fiber F1 is transmitted is corrected. That is, the refractive index dispersion is corrected.

[0008] As described above, in the optical transmission apparatus of this embodiment, between the optical fiber F1, F2, and deploy the optical parametric amplification device 10, amplified light O _sa and the idler by amplification using pump light O _p Since the configuration is such that the light O _i is generated and the idler light O _i is extracted by the filter 11, distortion due to the refractive index dispersion of the optical fibers F1 and F2 can be removed without using the optical amplifier 3 conventionally used. Thus, simplification of the apparatus can be realized, and economic efficiency is improved. Furthermore, optical parametric amplification device 10, it is possible to increase the idler light O _i exponentially, it is strongly light intensity with respect to the signal light O _s. That is, gain can be given to the idler light O _i , and transmission loss in the optical fiber F1 can be corrected. Note that the present invention is not limited to the above embodiment, and various modifications are possible. For example, in the above embodiment, the optical parametric amplifying element 10 is formed using AlGaAs.
It is also possible to use another semiconductor material such as P or a non-linear medium. For example, it can be formed of a ferroelectric material such as KTP or LiTaO ₃ . Furthermore, it is also possible to use an optical parametric amplification element 20 utilizing other principles such as four-wave mixing in a fiber, for example, and in this case, the same effects as those of the above embodiment can be obtained.

[0009]

As described above in detail, according to the present invention, the first optical fiber and the second optical fiber for bisecting the communication section for performing optical communication, and the signal light having the intensity of the pump light. An optical parametric amplification element that generates an amplified light and an idler light that is inverted in waveform with respect to the wavelength with respect to the signal light and the amplified light and amplified with the intensity of the pump light;
Since the optical transmission device is provided with a filter that selects only the idler light output from the optical parametric amplification element and outputs the selected idler light to the second optical fiber, the distortion due to the refractive index dispersion of the first and second optical fibers is removed. The optical transmission device can be simplified, and the economy is improved. Further, the optical fiber F
1, the transmission loss can be corrected.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical transmission device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a conventional optical transmission device.

[Explanation of symbols]

10 optical parametric amplification device 11 filters F1, F2 optical fiber O _s signal light O _sa amplified light O _i idler light

Claims (1)

[Claims] A first section for equally dividing a communication section for performing optical communication into two.
The signal light is input through the optical fiber and the second optical fiber and the first optical fiber, and the pump light is injected. The signal light is amplified using the optical parametric effect. An optical parametric amplifier that inverts a waveform related to wavelength with respect to the signal light and the amplified light and generates idler light amplified with the intensity of the pump light, and an output of the optical parametric amplifier. And a filter for selecting only idler light to be output and outputting the selected idler light to the second optical fiber.