JPH05224249A - Nonlinear optical device - Google Patents

Abstract

PURPOSE:To eliminate the walk-off of signal light and control light, to make the length of a nonlinear optical medium sufficiently long, and to reduce the operation power by equalizing the group velocity of the control light to that of the control light even unless the nonlinear optical medium in use has zero- dispersion wavelength in a wavelength range in use. CONSTITUTION:In the nonlinear optical device which is equipped with the optical medium having nonlinear refractive index effect and controls the intensity or direction of the signal light by using the control light, the optical medium is made of the nonlinear optical medium which has double refraction characteristics and the control light and signal light differ in wavelength and have their polarizing directions at right angles to each other. Further, the device may be equipped with an optical coupler 12 which has two incidence terminals and two projection terminals, the looped nonlinear optical medium 15 which is connected to the two, projection terminals, and an optical control means for propagating the control light in the nonlinear optical medium in one direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-linear optical device, and more specifically, in optical data / information processing, optical communication systems, etc., optical switches, optical memories, and optical signal arithmetic processing using these devices. The present invention relates to a non-linear optical device that is preferably used in a device or the like.

[0002]

2. Description of the Related Art In recent years, non-linear optical characteristics such as non-linear refractive index, non-linear absorption effect, electro-optic effect, second harmonic generation (SHG), etc. due to high-order polarization of substances such as glass materials and organic materials. It is expected that the nonlinear optical device and the nonlinear optical device using will be used for future optical communication and optical information processing systems. The non-linear optical effect, which is the operating principle of the above-mentioned non-linear optical device and non-linear optical device,
This is because the electric polarization P in the substance caused by the electric field E of light has a higher-order term proportional to E ² , E ³ etc. in addition to the term proportional to E as shown in the following formula (1). is there. P = χ ⁽¹⁾ · E + χ ⁽²⁾ · E ² + χ ⁽³⁾ · E ³ + ……… (1) where χ ⁽¹⁾ is the linear susceptibility and χ ⁽²⁾ and χ ⁽³⁾ are respectively It is called a second-order or third-order nonlinear susceptibility, the first term represents linear polarization, and the second and third terms represent second-order and third-order higher-order polarizations, respectively.

In particular, the third term brings about a change in the refractive index depending on the power density of light, which is expressed by the following equation (2), as is well known as the nonlinear refractive index effect. n = n ₁ + n ₂ | E | ² (2) The nonlinear refractive index n ₂ (m ² / v ² ) is equal to the ordinary refractive index n and the third-order nonlinear susceptibility χ ⁽³⁾ ( ³⁾ m ² / v ² ) and can be expressed as the following formula (3). n ₂ = 3/8 · n · χ ⁽³⁾ (3) where c is the speed of light and | E | is the average electric field of light. Various nonlinear optical elements can be constructed by using this effect, but in order to use this effect with smaller optical power, the power density of light is increased by a waveguide structure such as an optical fiber and long nonlinear optical elements are used. It is effective to increase the interaction length by using a medium.

Conventionally, as a non-linear optical device using an optical fiber, for example, KJBlow, NJDoran, BKNayar, and
A fiber loop mirror switch as shown in BPNelson OPTICS LETTERS Vol.15 p.248 (1990) is known. The nonlinear optical device of this type will be described below with reference to FIG.
Will be described. This non-linear optical device 1 is intended to control the destination of signal light having information, the waveform of signal light, etc. by another control light, and has two incident ends 2a, 2b and two emitting ends 2c, 2d, and an optical coupler 2 that splits the signal light S ₁ incident from one incident end 2a into two emission ends 2c and 2d substantially equally, and two emission ends 2c and 2d of the optical coupler 2. And a loop-shaped optical fiber (nonlinear optical medium) 3 having an optical nonlinear refractive index effect. The optical coupler 2 has a characteristic that the control light S ₃ incident from one incident end 2a is emitted from one emission end 2c.
₃ is configured to propagate in the optical fiber 3 having a nonlinear refractive index effect in only one direction.

Next, the operation of the nonlinear optical device 1 will be described. First, when the control light S ₃ is not incident, the signal light S ₁ incident from the one incident end 2a of the optical coupler 2 is demultiplexed substantially evenly by the optical coupler 2 and the optical fiber 3
The light propagates in the opposite directions to each other by exactly the same distance and returns to the optical coupler 2. In this optical coupler 2, the signal lights S ₁ and S ₁ propagating from both directions interfere with each other due to the interference effect in the optical coupler 2, and the signal light S ₁₃ is emitted from the incident end 2a.

On the other hand, the control light when the S ₃ is incident, the signal light S _1, the control light S ₃ of S ₁ propagating through the optical fiber 3
The signal light S ₁ propagating in the same direction as is subjected to the phase change due to the nonlinear refractive index effect based on the control light S ₃ .
This phase change amount ΔΦ is given by the following equation. ΔΦ = 4πn ₂ L | E | ² / λ (4) where L is the length (medium length) of the optical fiber 3, | E | is the average electric field of the control light S ₃ , and λ is the signal light S ₁ Is the wavelength of. Then, the amount of phase change Δ between the signal lights S ₁ and S ₁ propagating in the optical fiber 3 in opposite directions and returning to the optical coupler 2.
A phase difference of Φ occurs, and the signal light S ₁₄ is emitted from the other incident end 2b of the optical coupler 2 due to the interference effect. The ratio T of the signal light S ₁₄ emitted to the incident end 2b is given by the following equation. T = sin ² (ΔΦ / 2) (5) Therefore, if the control light S ₃ is incident so that the phase change amount ΔΦ becomes π, the signal is completely emitted from the incident end 2b.

[0007]

However, in the conventional nonlinear optical device 1, if a pulse having a very narrow width is used for the control light S ₃ in order to realize a high operating speed, the group velocity dispersion in the optical fiber 3 causes However, since the group velocities of the signal light S ₁ and the control light S ₃ which are pulsed lights are different from each other, there is a time lag between the two, which limits the length of interaction between the two. there were. This limited interaction length is commonly referred to as the walk-off effect, which limits the operating speed and power of this type of device.

The walk-off effect will be briefly described below. If the group velocities of the signal light S ₁ and the control light S ₃ are different, and the difference in time required for both to propagate in the optical fiber 3 is not negligible compared to the pulse width of the control light S ₃ , The phase change amount given by the above equation (4) is as follows. ΔΦ (t) = 4πn ₂ / λ · | E (t−Δτz) | ² dz (6) Here, the waveform of the control light S ₂ is a Gaussian function | E (t) | ² = | E ₀ | When expressed by ^{2 e t / T ... ... (} 7), the phase shift amount of the optical fiber 3 of length L [Phi is calculated by the following equation.

[Equation 1] Here, Δτ is the group delay difference per unit length between the signal light S ₁ and the control light S ₃ , and also the group delay T per unit length (the time required for the optical pulse to propagate a certain distance). ) Is the control light S
_When the half width of ₃ is τ, it is represented by τ / (2√1n2), and Γ is represented by t / Δτ. Further, E _rfc is a Gaussian error function. Here, for the sake of simplicity, the optical fiber 3
The propagation loss of is omitted.

FIG. 6 is a diagram for explaining the walk-off effect, and is a graph showing the time change of the equation (8), that is, the relationship between the switching speed and the phase change amount. Here, the pulse width of the control light is 4 ps, Δτ is 1 ps / m,
The length (medium length) L of the optical fiber 3 is set to 4, 8, 12, 16
There are 4 kinds of m. As can be seen from this figure, when there is a walk-off effect, even if the length L of the optical fiber 3 is increased, the effective interaction length is limited to T / Δτ, and the operation speed is controlled by the signal light. It is limited by the difference in group delay of light. Therefore, in a silica-based optical fiber that has been conventionally used as a non-linear medium, there are two wavelengths at which the group velocities are equal in the communication wavelength band (1.3 μm-1.55 μm), which is used for the walk-off. The effect had disappeared.

Generally, the difference in the velocity (group velocity) of an optical pulse propagating in an optical fiber depending on the wavelength (frequency) is known as group velocity dispersion. When the difference in the unit wavelength difference of the group delay T per unit length is defined as the group velocity dispersion D, this group velocity dispersion D can be expressed by the following equation. D = (1 / L) .delta.T / .delta..lambda. (9) The wavelength at which the group velocity dispersion D is 0 is called the zero dispersion wavelength. D is negative on the short-wave side and positive on the long-wave side. become. Since the zero-dispersion wavelength is in the communication wavelength band in the silica-based optical fiber, as shown in FIG. 7, there are two wavelengths having the same group delay on both sides of the zero-dispersion wavelength. Therefore, the walk-off effect is eliminated by selecting these wavelengths for the signal light and the control light.

However, since the non-linear refractive index of the silica-based optical fiber is extremely small, an optical fiber having a length of several 100 m to several km is required to realize a practical operating power, and a practical size is required. Making a device is extremely difficult. In order to solve this problem, various nonlinear optical materials with a larger nonlinear refractive index have been developed. Most of these materials have positive dispersion in the communication wavelength band (zero dispersion in this wavelength band). Since there is no wavelength), the wavelengths of the control light and the signal light must both be selected from the positive dispersion region, and it is impossible to make the group velocities of the two equal. Therefore, when a long optical fiber is used, there is a problem that the working speed and the working power are limited due to the walk-off effect.

As described above, in the conventional technique,
When control light, which is an optical pulse with a short wavelength, is used to achieve a high operating speed, when the optical fiber (nonlinear optical medium) used does not have a zero dispersion wavelength in the wavelength range used,
There is a problem that the group velocities of the signal light and the control light cannot be equalized, and the walk-off effect limits the operation speed and the operation power.

The present invention has been made in view of the above circumstances, and solves various problems and drawbacks of the related art, and a zero-dispersion wavelength in a wavelength range used by an optical fiber (nonlinear optical medium) used. A non-linear optical device that enables equalization of the group velocities of the signal light and the control light even if it does not have an optical path, does not cause a walk-off effect between them, and can operate at high speed and operates at low power. To provide.

[0014]

In order to solve the above problems, the present invention adopts the following non-linear optical device. That is, the non-linear optical device according to claim 1 comprises an optical medium having a non-linear refractive index effect, and in the non-linear optical device that controls either the intensity or the direction of the signal light using control light, the optical medium is The control light and the signal light have different wavelengths and their polarization directions are orthogonal to each other, which is made of a nonlinear optical medium having a characteristic of birefringence.

A nonlinear optical device according to a second aspect is
The non-linear optical device according to claim 1, wherein the non-linear optical device includes an optical coupler having at least two entrance ends and two exit ends, and a loop-shaped non-linear optical medium connected to the two exit ends of the optical coupler. And a light control means for propagating the control light in one direction in the nonlinear optical medium.

Further, the nonlinear optical device according to claim 3 is
The non-linear optical device according to claim 1, wherein the non-linear optical device includes first and second optical couplers having at least two incident ends and two outgoing ends, and two outgoing ends of the first optical coupler. Two optical media, which are respectively provided between the two incident ends of the second optical coupler and have the same optical length, and light control means for propagating the control light in the nonlinear optical medium are provided. The optical medium is characterized in that at least one of them is a non-linear optical medium having a characteristic of being birefringent.

[0017]

First, a method for matching the group velocities of the signal light and the control light according to the present invention will be described. FIG. 4 is a diagram for explaining the principle of matching the group velocities of the signal light and the control light, and is a diagram showing the wavelength dependence of the group delay per unit length. Generally, in an optical medium having a characteristic of birefringence, as shown in FIG. 4, the group velocity differs between the optical principal axis and the axis orthogonal thereto. This is called polarization dispersion. When the nonlinear optical medium is used at a wavelength apart from the zero-dispersion wavelength, if the same polarization is used for the control light and the signal light as in the conventional case, a difference in group delay occurs and the walk-off cannot be avoided. However, here, by setting the signal light and the control light to different polarizations (here, two types of x polarization and y polarization) and selecting the wavelengths of both so as to cancel the polarization dispersion, Both group delays can be matched.

In the non-linear optical device according to the first aspect of the present invention, the polarization directions of the signal light and the control light propagating in the non-linear optical medium having the characteristic of birefringence are made orthogonal to each other, and therefore the non-linear optical medium to be used. Even when the wavelength band used by does not have a zero-dispersion wavelength, the group velocities of the signal light and the control light can be made equal.

Further, in the non-linear optical device according to the second aspect, the polarization directions of the signal light and the control light propagating in one direction in the loop-shaped non-linear optical medium are orthogonal to each other, and therefore the non-linear optical device to be used is used. Even if the medium does not have a zero-dispersion wavelength in the wavelength range used, the group velocities of the signal light and the control light can be made equal.

In the non-linear optical device according to the third aspect, the signal light demultiplexed by the first coupler is propagated in one direction through the two non-linear optical media, and the control light is transmitted through the two non-linear optical media. Propagation is performed in the same direction as the signal light in a non-linear optical medium having a characteristic of birefringence among the optical media. During this propagation, the polarization directions of the signal light and the control light are orthogonal to each other, so even if the nonlinear optical medium used does not have a zero-dispersion wavelength in the wavelength range used, the group of the signal light and the control light It is possible to make the speeds equal.

[0021]

EXAMPLES Examples of the present invention will be described below. (First Embodiment) FIG. 1 is a diagram showing a non-linear optical device 11 according to the first embodiment of the present invention. This nonlinear optical device 11 is
The fiber couplers 12 to 14, an optical fiber (nonlinear optical medium) 15, and a light control means (not shown) are roughly configured.

The fiber coupler 12 has two entrance ends 1
2a and 12b and two emission ends 12c and 12d, and the signal light S ₅ incident from one incident end 12a is demultiplexed into the two emission ends 2c and 2d with a branching ratio of approximately 50%. ..

The fiber coupler 13 (14) is
It has two incident ends 13a, 13b (14a, 14b) and two emitting ends 13c, 13d (14c, 14d), and the signal light S ₅ is incident from one incident end 13a (14a).
Of the control light S ₆
It has a branching ratio of almost 100% with respect to the polarized wave of, and propagates the control light S ₆ in the optical fiber 15 in almost one direction. It is desirable that the optical fiber used in each of these fiber couplers 12 to 14 is a polarization maintaining type (PANDA) in order to stabilize the polarization direction in the interferometer.

As shown in FIG. 2, the optical fiber 15 is a chalcogenide glass (AS ₂ S ₃₎ having a non-linear refractive index of two digits larger than that of silica glass in order to operate at low power and to be a compact device. ), And is polarization-maintaining to match the group velocities.

The optical fiber 15 is composed of a core 21 and a clad 22, and the clad 22 is provided with stress applying portions 23, 23 at symmetrical positions with respect to the core 21. The signal light S ₅ and the control light S ₆ having a polarization orthogonal to the signal light S ₅ are set to have the same group velocity. Here, the dispersion value at the wavelength of the control light S ₆ is −660 ps / km · nm, and is designed to have a polarization dispersion of 3 ps / m for each polarization in the x-axis direction and the y-axis direction in the figure. Has been done.

Next, the operation of the nonlinear optical device 11 will be described. Here, the signal light S ₅ has a wavelength of 1.314 μm.
Optical pulse and control light S ₆ have a wavelength of 1.319 μm and a width of 2 p
An optical pulse of s is used, the polarization of the signal light S ₅ is in the y direction, and the polarization of the control light S ₆ is in the x direction, so that the group velocities of both are matched.

First, the incident end 13 of the fiber coupler 13
When the control light S ₆ is not incident on b, the signal light S ₅ incident on the incident end 12 a of the fiber coupler 12 is exactly the same in the optical fiber 15 by the interferometer configured by the optical fiber 15 and the fiber coupler 12. distance propagates in opposite directions, and returns to the incident end 12a as the signal light S ₅₁ which is not switched.

On the other hand, the incident end 13 of the fiber coupler 13
When the control light S ₆ is incident on b, the signal light S ₅ incident on the incident end 12 a of the fiber coupler 12 is evenly demultiplexed by the fiber coupler 12. Since the signal light S ₅ which proceeds in the same direction overlapping the middle of which optical fiber 15 of the signal light S _5, S ₅ and the control light S ₆ is subjected to phase modulation by the nonlinear refractive index effects, the interference effect in the fiber coupler 12 The switched signal light S ₅₂ is emitted from the incident end (signal light emitting end) 12b.

Therefore, if the signal light emitting end 12b is used, the intensity of the signal light S ₅ passing therethrough can be controlled by changing the control light S ₆ . In addition, the incident end 1
2a is also used as the signal light emitting end, so that the direction of the signal light S _{5 can be changed} depending on the intensity of the control light S _6.
2b or the signal light incident end 12a can be switched.

In the above nonlinear optical device 11, the signal light S
_In order to give a phase change of π to ₅ for complete switching, a control light S _{6 having} a peak power as given by the following equation is used.
Will be required. P = 3λA _eff / (4n ₂ L) (10) where A _eff is the effective core area and n ₂ is the nonlinear refractive index defined by (m ² / w). Here, the effective core cross-sectional area of the optical fiber 15 is 6 μm ² , and the fiber length L is 15
m. Further, n ₂ of chalcogenide glass (AS ₂ S ₃ ) which is the main component of the optical fiber 15 is 4.2 × 10.
^-18 (m ² / w).

This value is an extremely small value for this type of device, and a longer medium, or a larger n.
_If a material having ₂ is used, it is possible to further reduce the operating power.

In the above nonlinear optical device 11, π
The peak power of the control light S ₆ required to change the phase of is 94m
It was W. Further, by using the control light S ₆ having a width of 8 ps, an operating speed of 10 ps could be obtained.

As described above, according to the non-linear optical device 11 of the above-described embodiment, the polarization directions of the signal light S ₅ and the control light S ₆ propagating in one direction through the loop-shaped optical fiber 15 are changed. They can be made orthogonal to each other, and the group velocities of the signal light S ₅ and the control light S ₆ can be made equal even if the optical fiber 15 used does not have a zero-dispersion wavelength in the wavelength range used. Therefore, the walk-off of the signal light S ₅ and the control light S ₆ does not occur, the length of the optical fiber 15 can be made sufficiently long, and the operating power can be reduced. Further, this can also increase the operating speed.

Moreover, since it has a switching speed of 10 ps, it has a modulation function of modulating the signal light at 100 GHz, and a demultiplexer for extracting an arbitrary signal pulse from a signal light pulse train having a repetition frequency of 100 GHz and converting it into a low repetition pulse train. It is possible to realize a multiplexing function, a multiplexing function for multiplexing several low-repetition optical pulse trains into a 100 GHz optical pulse train, and the like.

As described above, it is possible to realize a non-linear optical device that can operate at high speed and operate with low power.

As a device having the same effect as the nonlinear optical device 11 of the above embodiment, the optical fiber 3 in the conventional nonlinear optical device 1 is replaced with the optical fiber 15 of the nonlinear optical device 11, and the signal light has a wavelength of 1 It can also be realized by using an optical pulse of .314 μm and a control light as an optical pulse having a wavelength of 1.319 μm and a width of 2 ps and making the polarization directions of the two orthogonal to each other. However, in this case, the yield of the optical coupler 2 is 50 with respect to the polarization of the signal light.
%, And 0% with respect to the polarization of the control light.

(Second Embodiment) FIG. 3 is a diagram showing a non-linear optical device 31 according to a second embodiment of the present invention. In the non-linear optical device 31 of FIG. 3, the same components as those of the non-linear optical device 11 of FIG.
The non-linear optical device 31 has a Mach-Zehnder interferometer type configuration and includes fiber couplers 13, 14, and 3.
2, 33, optical fibers (non-linear optical medium) 15, 34,
It is roughly configured by a light control means (not shown).

The fiber couplers 32 and 33 have two entrance ends and two exit ends, and demultiplex the signal light entering from one entrance end at a branching ratio of about 50%. The optical fiber 34 is an optical fiber having the same optical length as the optical fiber 15.

Next, the operation of the nonlinear optical device 31 will be described. Here, the signal light S ₇ has a wavelength of 1.314 μm.
Optical pulse, control light S ₈ has a wavelength of 1.319 μm and a width of 2 p
An optical pulse of s is used, the polarization of the signal light S ₇ is in the y direction, and the polarization of the control light S ₈ is in the x direction, so that the group velocities of both are matched.

First, the incident end 13 of the fiber coupler 13
When the control light S ₈ is not incident on b, the signal light S ₇ incident on the incident end 32a of the fiber coupler 32 is a signal that is not switched by the interferometer configured by the optical fibers 15 and 34 and the fiber couplers 13 and 14. The light S ₇₁ is emitted from the emission end 33a.

On the other hand, the incident end 13 of the fiber coupler 13
When the control light S ₈ is incident on b, the signal light S ₇ incident on the incident end 32 a of the fiber coupler 32 is evenly demultiplexed by the fiber coupler 32. Since the signal light S ₇ traveling in the same direction overlapping the middle of which optical fiber 15 of the signal light S _7, S ₇ and the control light S ₈ is subjected to phase modulation by the nonlinear refractive index effects, the interference effect in the fiber coupler 15 The switched signal light S ₇₂ is emitted from the emission end 33b.

Therefore, if the emitting end 33b is used, the intensity of the signal light S ₇ passing therethrough can be controlled by changing the control light S ₈ . Further, by using the emitting end 33a as well, the signal light S _{7 is changed} depending on the intensity of the control light S _8.
The direction can be switched to the emission end 33b or the emission end 33a.

Also in the above-mentioned nonlinear optical device 31, π
The peak power of control light S ₈ required to change the phase of
An operating speed of 10 ps could be obtained by using the control light S ₈ having a width of 8 ps and having a width of 8 ps.

As described above, the non-linear optical device 31 of the above embodiment can also provide the same operation and effect as the non-linear optical device 11 of the first embodiment.

[0045]

As described above, according to the non-linear optical device of the first aspect of the present invention, an optical medium having a non-linear refractive index effect is provided, and the intensity or direction of the signal light is controlled by using the control light. In the non-linear optical device for controlling the above, the optical medium is made of a non-linear optical medium having a characteristic of birefringence, and the control light and the signal light have different wavelengths and their polarization directions are orthogonal to each other. Therefore, the polarization directions of the signal light and the control light propagating in the nonlinear optical medium having the property of birefringence can be made orthogonal to each other,
Even if the nonlinear optical medium used does not have a zero-dispersion wavelength in the wavelength range used, the group velocities of the signal light and the control light can be made equal. Therefore, the walk-off of the signal light and the control light does not occur, the length of the nonlinear optical medium can be made sufficiently long, and the operating power can be reduced. Further, this can also increase the operating speed.

According to a second aspect of the present invention, there is provided a non-linear optical device according to the first aspect, wherein the non-linear optical device includes an optical coupler having at least two entrance ends and two exit ends. Since the loop-shaped nonlinear optical medium connected to the two emission ends of the optical coupler and the optical control means for propagating the control light in the nonlinear optical medium in one direction are provided, the loop In the case where the polarization directions of the signal light and the control light propagating in one direction in a linear optical medium can be made orthogonal to each other, and the nonlinear optical medium used does not have a zero-dispersion wavelength in the wavelength range used. Even if there is, the group velocities of the signal light and the control light can be made equal. Therefore, the walk-off of the signal light and the control light does not occur, the length of the nonlinear optical medium can be made sufficiently long, and the operating power can be reduced. Further, this can also increase the operating speed.

According to a third aspect of the present invention, there is provided the first non-linear optical device according to the first aspect, wherein the first non-linear optical device has at least two entrance ends and two exit ends. Of the optical coupler and the two emitting ends of the first optical coupler and the two incident ends of the second optical coupler, each having an equal optical length.
Optical medium, and a light control means for propagating the control light in the nonlinear optical medium, wherein the optical medium is
Since at least one of the nonlinear optical media has a characteristic of birefringence, the signal light demultiplexed by the first optical coupler is propagated in the two nonlinear optical media in one direction, and the control light is transmitted. To propagate in the same direction as the signal light through the nonlinear optical medium having the characteristic of birefringence among the two nonlinear optical media, and make the polarization directions of the signal light and the control light orthogonal to each other during this propagation. Therefore, even if the nonlinear optical medium used does not have a zero-dispersion wavelength in the wavelength range used, the group velocities of the signal light and the control light can be made equal. Therefore, the walk-off of the signal light and the control light does not occur, the length of the nonlinear optical medium can be made sufficiently long, and the operating power can be reduced. Further, this can also increase the operating speed.

As described above, it is possible to realize a non-linear optical device which can operate at high speed and operate with low power.

[Brief description of drawings]

FIG. 1 is a diagram showing a non-linear optical device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an optical fiber that is a nonlinear optical medium of the nonlinear optical device of the first embodiment of the present invention.

FIG. 3 is a diagram showing a non-linear optical device according to a second embodiment of the present invention.

FIG. 4 is a diagram showing wavelength dependency of group delay per unit length for explaining the principle of coincidence of group velocities of signal light and control light.

FIG. 5 is a diagram showing a conventional nonlinear optical device.

FIG. 6 is a diagram showing a relationship between a switching speed and a phase change amount for explaining a walk-off effect.

FIG. 7 is a diagram showing dispersion characteristics of a conventional silica optical fiber.

[Explanation of symbols]

11 Nonlinear Optical Device 12 Fiber Coupler 12a, 12b Incident End 12c, 12d Emitting End 13 Fiber Coupler 13a, 13b Incident End 13c, 13d Emitting End 14 Fiber Coupler 14a, 14b Incident End 14c, 14d Emitting End 15 Optical Fiber (Nonlinear Optical Medium ) 21 core 22 clad 23 stress applying part 31 non-linear optical device 32 fiber coupler 32a entrance end 33 fiber coupler 33a, 33b exit end 34 optical fiber S ₅ signal light S _{51 non-} switched signal light S ₅₂ switched signal light S ₆ control Light S ₇ Signal light S ₇₁ Signal light not switched S ₇₂ Signal light switched ₇ S ₈ Control light

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenichi Kuboji 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (3)

[Claims] 1. A non-linear optical device comprising an optical medium having a non-linear refractive index effect, wherein the control light controls either the intensity or the direction of the signal light, wherein the non-linear optical device has a characteristic of birefringence. A non-linear optical device comprising an optical medium, wherein the control light and the signal light have different wavelengths and their polarization directions are orthogonal to each other. 2. The non-linear optical device comprises: an optical coupler having at least two entrance ends and two exit ends; a loop-shaped non-linear optical medium connected to the two exit ends of the optical coupler; and the control light. 2. A non-linear optical device according to claim 1, further comprising a light control means for propagating the light in the non-linear optical medium in one direction. 3. The non-linear optical device comprises: first and second optical couplers having at least two incident ends and two emitting ends; two emitting ends and a second optical coupler of the first optical coupler. Two optical media having the same optical length and provided between the two incident ends of the optical control means and the optical control means for propagating the control light in the nonlinear optical media. 2. A non-linear optical medium at least one of which has a characteristic of birefringence.
The described nonlinear optical device.