JPS6197630A - Logical element of optical fiber - Google Patents

Abstract

PURPOSE:To obtain an optical logical element which is operated by an optical signal only and high in responding speed and reliability, by synthesizing two optical pulses and making the result incident to a polarized light maintaining optical fiber at a plane of polarization angle of other than 45 deg. from the main axis of the fiber, then, detecting the outgoing light by means of an analyzing element. CONSTITUTION:Pulse light coming out from a light source 11 are divided into two parts by means of a half mirror 4 and the one part reflected by the mirror 4 is passed through an attenuator 5 and synthesized with the other part transmitted through the mirror 4 at another half mirror 4. Then the plane of polarization of the optical pulse is adjusted to the main axis of the double refraction of an optical fiber 7 (at an angle of other than 45 deg. from the main axis) and the optical pulse is made incident to the polarized light maintaining optical fiber 7 after the optical pulse is stopped by an objective lens 6. Outgoing pulses are made incident to an analyzer 8 and, when the input optical pulse to the fiber 7 is weak, transmitted light is extinguished.. When the input optical pulse is strong, the plane of polarization is turned in the fiber 7 and the outgoing lights pass through the analyzer 8 and are detected by a photodetector 10. Therefore, AND operation (a monochromator 9 is not required) is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fiber element for optical logic operations that performs optical input-optical output logic operations using nonlinear optical effects occurring in optical fibers. be.

(Prior art) Conventionally, this type of element uses a Farpry-Perot resonator,
Saturable absorption characteristics or optical power inside the resonator (Kerr
) By inserting a medium that also has an effect, logical operations were performed using the optical bistable operation obtained there.

(Problem to be solved by the invention) However, since the Fabry-Perot resonator is used, high precision is required in selecting the resonator length and aligning the mirror, and the resonator itself is large and inconvenient to handle. It had a drawback.

(Means for Solving the Problems) One feature of the present invention is that a polarization maintaining optical fiber, two optical input ends, a means for multiplexing input pulse light from the input ends, and a multiplexing optical fiber are provided. The input pulsed light is linearly polarized, and the main axis of the polarization-maintaining optical fiber is connected to the polarization-maintaining optical fiber. an optical fiber logic element consisting of a means for optically coupling at an angle other than that of the polarization maintaining optical fiber, an analyzer for analyzing the light emitted from the polarization maintaining optical fiber, and an output end for taking out the output from the analyzer. be.

(Function) With the above configuration, logical operations such as logical product, logical sum, and negation can be performed using the optical force effect, and an optical logic element with high speed operation and high reliability can be obtained.

(Example) Figure 1 is a block diagram of an experiment conducted to confirm the operation of the optical fiber logic element of the present invention. Pulse light from a single light source 1) is separated into two by a half mirror 4. It is combined again and input into the optical fiber.

1 is optical input pulse ■, 2 is prior input pulse ■, 3 is λ/2
Plate phase shifter, 4 is a half mirror, 15 is an attenuator, 6 is an objective lens, 7 is a polarization maintaining optical fiber, 8 is an analyzer (Glantom Soy prism), 9 is a monochromator, 1O is a photodetector, 1) is a light source. To perform an AND (logical product) operation in this system, the polarization plane of the optical input pulses ① and ② is passed through the phase shifter 3, and the polarization plane of the incident light is aligned with the principal axis of birefringence of the optical fiber 7, and the objective lens 60 is used. It is focused and introduced into an optical fiber. Since the polarization direction of the incident light is the same as that of the main axis of the optical fiber 7, the AND of the present invention
The action is not realized. At this time, it is necessary that the optical input pulses ■ and ■ have the same phase with each other and have a sufficiently long coherent length, or the coherent length must be sufficiently short compared to the optical path length difference between the two human input signals so that no interference occurs. be. Furthermore, in the configuration shown in Figure 1, the delay time difference due to the difference in optical path length between the two operators corresponds to the time difference between the pulses incident on the two input terminals of the element of the present invention, and this must be sufficiently short compared to the input optical pulse width. No. When the light intensity of the light pulse incident on the optical fiber 7 is strong, the polarization state of the input light pulse changes after propagation through the optical fiber due to the light intensity dependence of birefringence caused by the optical force effect. . If the analyzer in step 8 is adjusted so that the transmitted light is quenched when the input optical pulse intensity is sufficiently weak, the plane of polarization will rotate when the optical pulse intensity is strong, causing part of the optical pulse to disappear. The light passes through 8 analyzers and is received by 10 photodetectors. However, in the AND operation, the 9 monochromators are not necessary. In order to obtain the above-mentioned birefringence characteristics that depend on the light intensity, the polarization plane of the incident light must be
It must be incident at an angle other than 45°,
The larger the deviation of the incident light from the principal axis of the optical fiber, the more nonlinearity of the output power appears from a low input light power.

FIG. 2 shows experimental results showing the power of the analyzer-transmitted light pulse caused by the above-mentioned nonlinear optical effect with respect to the incident power. The light source is Nd: YAG with a Q switch added.
It is a laser, the oscillation wavelength is 1000 μm, and the polarization plane of the input optical pulse is made to coincide with the main axis of the fiber. Note that the tree polarization maintaining fiber is an elliptical core single mode fiber with a fiber length of 1) m. The optical pulse output is proportional to the cube of the power of the input optical pulse. In Figure 2, for example, if the peak power of the input optical pulse is LOW, when only one of the inputs is input, the transmitted optical power is about 0.9 on the arbitrary scale of the vertical axis, but the optical pulses with equal intensity mutually When both are input at the same time, the input power is 20W, so the output is about 7. This situation is schematically shown in FIG. 3. Therefore, the optical power generated in the optical fiber −
By utilizing the light intensity dependence of birefringence due to the effect, that is, the phenomenon in which the plane of polarization rotates according to the light intensity, a logical AND operation can be performed between two input light pulses and a transmitted light pulse.
Can perform movements. FIG. 4 shows experimental data for this AND operation. ia) shows, from the left, the pulse waveforms of the light transmitted through the analyzer for input optical pulses only, input optical pulses only, and inputs ■+■, respectively. The states of only input optical pulses (■) and (2) were realized by blocking one of the optical paths in FIG. 1. The peak power of each input optical pulse is 30 W, and the input pulse waveform is as shown in FIG. 4(C). The output peak value for the input ■+■ was approximately 10 times the "O1" level (OFF' state) shown in Figure 4 (a), and this was considered to be the 1" level (ON state). The 0N10FF ratio at that time was approximately 10 times higher. On the other hand, the peak value of the input optical pulse is extremely low at 0.3 W.
Figure 4 (In the case of bl, the peak value of the output pulse for the input
No action is possible.

Next, the OR operation shown in FIG. 5 requires saturation of the optical output. Attenuation of the input optical pulse by stimulated Raman scattering can be used as one method to obtain this saturation characteristic. Figure 6 shows 5.5 m of other types of polarization maintaining fiber (PANDA
According to the experimental results of the optical fiber), the power of the input optical pulse is 30
At 0 W or more, the transmitted light intensity becomes saturated. Furthermore, even if the incident intensity is increased, the input power will shift to Stoke's light of stimulated Raman scattering, so if you select the wavelength of the analyzer transmitted light with a monochromator and receive only the power of the input light wavelength, the transmitted light intensity will remain constant. OR because it will not exceed the value.

It can be seen that the required pre-input Kerr light output characteristics suitable for operation are actually obtained. FIG. 7 shows the experimental results of the transmitted light pulse waveform of this PANDA fiber, and clearly saturation is seen in the output pulse waveform for input powers of 330 W and 480 W at the fiber length of 5.5 m in (b).

Figure 8 shows a case in which the element capable of AND operation is composed only of optical fibers, and numeral 12 acts as an analyzer (absolutely single polarization maintaining optical fiber). If a wave laser beam is used, the polarization plane of the incident light and the main axis of the fiber can be made to coincide by rotating the polarization-maintaining fiber 7, so the λ plate retarder at the input end of the optical fiber 7 can be removed. A monochromator after the analyzer is also unnecessary in the case of AND operation because the influence of stimulated Raman scattered light can be ignored, so the configuration shown in Figure 8 is possible. Figure 9 shows absolute single polarization. This is a cross-sectional view of a storage fiber (PANDA fiber), in which 13 is a core and 14 is a stress-applying part.The measured values of the bending loss wavelength characteristics of two orthogonal polarized waves of this fiber are shown in Fig. 10.Bending diameter is approximately 40 mmφ and the fiber length is approximately 10 m.The wavelength of the Nd:YAG laser light source used in this experiment is 1
, 064 μm, almost no Y-axis polarized waves are transmitted, and only X-axis polarized waves are transmitted, so this fiber can be used as an analyzer by connecting the main axis of the polarization-maintaining fiber in step 7 with the main axis of this fiber. be able to. 1) Figure (
Figures a) and (b) show experimental values of AND operations in all fiber elements connected to 2 m and 6 m elliptical fibers and this fiber analyzer. (a), (bl) Both results were obtained using a Glan-Thompson prism as an analyzer (Fig. 4 (
Compared to a)), almost the same ON10 FF ratio was obtained, and an all-fiber AND element was realized.

(Effects of the Invention) As explained above, this optical arithmetic element does not use any electrical signals and operates only with optical signals, so the electronic circuit can be eliminated, and the optical force-effect response is 10"bit/s. Because it is very fast and extremely fast, it enables a high-speed response, and since it does not use a Farpley-Perot resonator, it can improve the reliability of the device.In particular, all-optical fiber devices can easily connect devices with optical fibers, so they are less susceptible to problems that occur in electronic circuits. Furthermore, since it uses optical fiber, it is resistant to external disturbances such as electromagnetic induction (and has the advantage of being small and lightweight).
It is promising as an optical logic operation element to be used in future optical computers.

Furthermore, although this example shows an example using a silica-based optical fiber, the threshold value of the input optical power can be reduced by making the fiber into a material whose optical power-effect constant is larger than that of the silica-based fiber. .

Among the fibers that have actually been realized, for example, germanium core fiber has a carbon content of about 10 times that of silica fiber.
Some 82-filled liquid core fibers have optical power-effect constants of about 200.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the device of this example, Figure 2 is a diagram showing optical input/output characteristics, Figure 3 is a schematic diagram of AND operation, and Figure 4 is A
Figure 5 shows the experimental results of ND operation, Figure 5 is a schematic diagram of OR operation, Figure 6 shows the optical input/output characteristics with saturation, Figure 7 shows the transmitted light pulse waveform, and Figure 8 shows the entire fiber element. Fig. 9 is a cross-sectional view of an absolutely single polarization maintaining fiber, No. 1O
The figure shows the bending loss wavelength characteristics of X and Y polarized waves, and Figure 1) shows the experimental results of AND operation of all fiber elements. l...First-in Cajals■, 2...First-in Cajals■,
3...λ/2 plate retarder, 4...Half mirror 1
5... Attenuator, 6... Objective lens, 7
...Polarization maintaining fiber, 8...Analyzer (Glan-Thompson prism), 9...
Monochromator, 10... Photodetector, 1)... Light source, 12... Fiber analyzer, 13...
... Core, 14... Stress applying part.

Claims (4)

[Claims] (1) A polarization-maintaining optical fiber, two optical input ends, a means for combining the input pulsed light from the input ends, and a main axis and a 45-degree polarization-maintaining optical fiber. °
means for optically coupling at an angle other than the above, an analyzer that analyzes the light emitted from the polarization-maintaining optical fiber as it is or after converting it into linearly polarized light, and an output end that takes out the output from the analyzer. An optical fiber logic element comprising: (2) The optical fiber logic element according to claim 1, wherein the analyzing element is an analyzer and performs an AND operation. (3) The analysis element consists of an analyzer and a monochromator, and
The optical fiber logic element according to claim 1, characterized in that it performs R operation. (4) The optical fiber logic device according to claim 1 or 2, wherein the analyzer is a fiber analyzer.