JPH03225328A - Optical frequency converter - Google Patents

Abstract

PURPOSE:To set the shifting quantity of a conversion frequency from several GHzs to thousands of GHzs by multiplexing two pump light beams with input light and amplifying and filtering them, and further multiplexing, amplifying, and filtering 3rd pump light. CONSTITUTION:An optical multiplexer 3 multiplexes the pump light beams from 1st and 2nd pump light sources 1 and 2 with the input light and then a semiconductor amplifier 4 amplifies them. Then a filter 5 transmits a component of the amplified light which is in the vicinity of the frequency of the 2nd pump light and interrupts a component of frequency which is in the vicinity of that of the 1st pump light. Further, an optical demultiplexer 7 multiplexes the pump light of a 3rd pump light source 6, a semiconductor optical amplifier 8 amplifies the light, and then an optical fiber 9 filters the amplified light at a periodic resonance frequency. Consequently, the shifting quantity of the conversion frequency can be set to a large value from several GHzs to thousands of GHzs.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical frequency conversion device that converts an input optical frequency to another frequency and outputs the same.

(Prior Art) Conventionally, methods for converting the input optical frequency include (1) a method using second or third harmonic generation of a nonlinear optical element, and (2) frequency increase conversion using a parametric effect. , (3) A method of shifting the frequency by interaction with an acoustic wave excited in an acousto-optic element, (4) A method using near-degenerate four-wave mixing in a semiconductor optical amplifier (IEICE technical research report by Kobe et al. 0QE88-34. For details, refer to the published literature), (5) Modulate the second pump light by carrier density fluctuation excited by the beat frequency of the first pump light input to the semiconductor optical amplifier and the input signal light. Method (Groskop et al., Electronics Letters Vol. 24, No. 17, pp. 1106-1107 (1)
988) is known in detail.

(Problems to be Solved by the Invention) In order to apply an optical frequency conversion device to an actual system, for example, a frequency division optical switching system, it is necessary to: ■ obtain a relatively high conversion efficiency; It is necessary to satisfy conditions such as being able to convert between frequencies.

Among the above conventional methods, method (1) uses 2 of the input optical frequency.
Sweeping the output optical frequency is not possible, only doubling or tripling the frequency. In method (2), although the output optical frequency can be swept, sufficient conversion efficiency cannot be obtained.

Furthermore, in methods (3) and (4), the sweep range of the output optical frequency is limited to about I GHz and about 10 GHz, respectively. In method (5), although the sweep range can be widened, the input optical frequency and the converted frequency cannot be made close to each other, and therefore the above condition (2) cannot be found. As described above, each of the conventional optical frequency conversion devices has problems that must be solved when applied to an optical frequency division optical conversion system or the like.

Therefore, an object of the present invention is to solve the above problems and
It is an object of the present invention to provide a frequency conversion device that is capable of converting between a plurality of frequencies arranged at intervals of about GHz and has high conversion efficiency.

(Means for Solving the Problems) Means provided by the present invention to solve the above-mentioned problems are as follows:
first and second pump light sources that output first and second pump lights, respectively; and external signal light having a frequency approximately equal to the first and second pump lights and the first pump light. A first optical multiplexer to combine, a first semiconductor optical amplifier into which the output light of the first optical multiplexer is input, and a second pump of the output light of the first semiconductor optical amplifier. a first optical filter that transmits frequency components near the optical frequency and blocks frequency components near the first pump light frequency; a third pump light source that outputs a third pump light; a second optical multiplexer that multiplexes the pump light and the output light of the first optical filter; a second semiconductor optical amplifier that receives the output light of the second optical multiplexer; The present invention is an optical frequency conversion device characterized in that it includes a second pre-filter having a periodic resonance frequency that filters output light from a semiconductor optical amplifier.

(Operation) In the present invention, carrier density fluctuation is caused at the beat frequency between the input light to the first semiconductor optical amplifier and the first pump light, and a replica of the input light spectrum is generated near the frequency of the second pump light. cause Furthermore, the replica of the input light amplified by the first semiconductor optical amplifier and the second pump light are combined with the third pump light and inputted to the second semiconductor optical amplifier. A similar phenomenon occurs, and the input optical spectrum is shifted to near the frequency of the third pump light. By setting the frequency arrangement of the first and third pump lights as shown in FIG. 2, the input optical frequency can be moved to another frequency separated by about several tens of GHz. That is, the present invention allows conversion between a plurality of frequencies arranged at intervals of about 10 GHz. Furthermore, since the present invention uses an amplification medium as a nonlinear element, a conversion efficiency of 1 or more can be easily obtained.

(Example) Hereinafter, the present invention will be explained in more detail with reference to Examples.

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

In this embodiment, a case will be described in which conversion is performed between adjacent channels among a plurality of frequency channels arranged at intervals of 15 GHz.

The emitted light from 1 and 5 μm band distributed feedback semiconductor lasers (DFB) 1 and 2 used as the first and second pump light sources is as follows:
The input light is multiplexed with the first optical multiplexer 3 and input to a first semiconductor optical amplifier (LD amplifier) 4 having a gain peak in the 1.5 μm band.

The frequency difference between DFBI and 2 is set to 1000 GHz,
The frequency difference between the input light and the first DFBI is set to 5G)Iz. The output optical spectrum of the first LD amplifier 4 is shown in FIG. As shown in this figure, in the output light of the LD amplifier 4, the input light spectrum appears on both sides of the frequency of the DFB 2.

The output light from the LD amplifier 4 is input to the first optical filter 5 at the next stage. The optical filter 5 is a dielectric multilayer interference filter having transmission characteristics as shown in FIG. The output light of
incident on . The frequency of DFB6 is set to be 15 GHz lower than the frequency of DFBI.

The output light spectrum of the LD amplifier 8 is shown in FIG.

As shown in this figure, in the output light of the LD amplifier 8, the input light spectrum has shifted to a position 5 GHz away from the frequency of the DFB 6, which is the third pump light.

Finally, the output light from the LD amplifier 8 is input to a second optical filter 9. The optical filter 9 has a fleece vector range and finesse of 15 GHz and 20, respectively.
This is a Fapley-Perot etalon with adjusted thickness and end face reflectance.

By the above operations, output light appears on the 15 GHz low frequency side of input light. Only this component appears at the output and is blocked by another second filter 9.

In this embodiment, the input light is shifted to the lower frequency side of 15 GHz, but by changing the frequency of the third DFB 8, the frequency after conversion can be freely selected.

(Effects of the Invention) As described above, the present invention can provide an optical frequency conversion device that can arbitrarily set the shift amount of the conversion frequency from a small value of about several GHz to a large value of several 1000 GHz. Furthermore, since the present invention uses a nonlinear optical effect using an amplification medium, high conversion efficiency can be easily achieved.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention, FIG. 2 is a spectrum diagram showing the positional relationship of each pump light and the obtained converted light,
Figure 3 shows the four-output optical spectrum of the first LD amplifier and the first
FIG. 4 is a diagram showing the transmission characteristics of the optical filter 5 of
Output optical spectrum of D amplifier 8 and second optical filter 9
FIG. 1.2.6... 1.5 μ-band distributed feedback semiconductor laser, 3.7... Optical multiplexer, 4, 8... Semiconductor optical amplifier, 5.9... Optical filter.

Claims (1)

[Claims] first and second pump light sources that output first and second pump lights, respectively; and external signal light having a frequency approximately equal to the first and second pump lights and the first pump light. A first optical multiplexer to combine, a first semiconductor optical amplifier into which the output light of the first optical multiplexer is input, and a second pump of the output light of the first semiconductor optical amplifier. a first optical filter that transmits frequency components near the optical frequency and blocks frequency components near the first pump light frequency; a third pump light source that outputs a third pump light; a second optical multiplexer that multiplexes the pump light and the output light of the first optical filter; a second semiconductor optical amplifier that receives the output light of the second optical multiplexer; An optical frequency conversion device comprising: a second optical filter having a periodic resonance frequency that filters output light from a semiconductor optical amplifier;