JPH07508355A - Improvement of optical phase shifter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Improvement of optical phase shifter Technical field The present invention encompasses phase shifters, isolators, circulators, and two-way communication devices. The present invention relates to an optical device including the present invention. In more detail, however, it is not limited to However, the present invention relates to fiber optic communication devices.

Background technology Optical isolators are used in many optical devices, including communications applications and solid state lasers. It is an important part in the installation. The role of an isolator is to allow light to flow in only one direction. The goal is to make it possible for the information to propagate. Using isolators in communication equipment This allows the laser diode to retune due to feedback resulting from reflection. and can be used with optical amplifiers to reduce laser action due to feedback. Alternatively, it can be ensured that deterioration due to noise does not occur. A typical amplifier is A conventional isolator at its input, or at its output, or at both its input and output. will have data. Do not use an isolator due to residual reflections and scattering. It is practically impossible to operate an amplifier with very high gain.

Most conventional isolators of the prior art obtain non-reciprocal rotation of the polarization state of light. The Faraday effect is used for this purpose. When a magnetic field is applied, the plane of polarization of light changes the direction of propagation. Rotates independently of direction. The rotation of the plane of polarization of light depends on the material through which the light is propagating. It is proportional to the Verdet constant of the material. By using a crystal with a large Verdet constant, , a 45 degree rotation can be achieved in a short distance. A single polarization isolator is It can be configured as shown in FIG. Light traveling from left to right is vertical It is polarized and then rotated by 45 degrees by a Faraday rotator. Second polarizer are placed at a 45 degree angle, allowing light to pass through undisturbed. Wear. Light traveling from right to left is polarized in a 45 degree direction and then undergoes Faraday rotation. Rotate an additional 45 degrees by the child. Therefore, the plane of polarization of light is horizontal Will. This light is completely blocked by the nail direct polarizer and is therefore directed from right to left. No light will pass in the opposite direction.

One technique to obtain polarization-independent separation is to separate the incident light into two polarization components; Separate each of these components and then recombine the two polarized components. This is a method to The polarization splitter itself is made as a polarizer for the isolator. can be used and is therefore polarization independent, as shown in Figure 2. An isolator can be configured.

Although such isolators are essential in many amplification applications, The isolator has the possibility of carrying 4G in two directions with one fiber, and Denies the possibility of amplification. In a device using an optical amplifier, a single fiber in two directions It is desirable to be able to obtain communications.

One object of the invention is to provide an improved system which at least ameliorates the drawbacks of the prior art. is to obtain a solatator.

According to one feature of the present invention, the rotation direction of the polarization plane depends on the propagation direction of the transmitted light. at least one first polarization plane rotating device; at least one device for changing the plane of polarization; Virtually half of all light propagating from both ends of the plane with any plane of polarization is the first polarization. passing through each of the plane rotation device and the second device for changing the plane of polarization; A non-reciprocal phase shifter is obtained.

According to yet another feature, the invention provides a method for transmitting incident light through a first optical path and a second optical path. and a device for recombining the optical paths at the output, and the optical paths have an arbitrary polarization. a first device and a second device, respectively, for changing the plane of polarization of incident light having light; and at least one of said devices for changing the plane of polarization in a first propagation direction. a first rotation relative to the direction of propagation and a second rotation relative to the second propagation direction; Change the plane of polarization independent of the propagation direction at the other or one of the Sk positions to ,and a first relative phase change between the optical paths occurs for light propagating in a first direction; a second relative phase change between or is configured to occur for light propagating in a second direction It also has an optical non-reciprocal transfer device.

According to still further features, the invention provides a method for transmitting incident light through a first optical path and a second optical path. a device for transporting and recombining the optical paths at an output, and wherein the first optical path is a first optical path. A first polarization plane rotation device that performs rotation depending on the propagation direction in one propagation direction and the propagation direction. a second polarization plane changing device that changes the plane of polarization independently of the second optical path; a third polarization plane changing device that changes the first propagation direction independently of the propagation direction; and a fourth polarization plane device that rotates depending on the propagation direction, and substantially half propagates through each of said first optical path and said second optical path, and An optical non-reciprocal phase shifter is used in which the relative phase change of the output light depends on the propagation direction of the incident light. do.

Yet another feature of the invention provides that substantially half of the incident light can be filtered, each with an arbitrary plane of polarization. propagating through two optical paths with a device for changing the plane of polarization of light propagating in each of the optical paths; and outputting an output having a first relative phase change in a "first" propagation direction of the light beam. said optical path has outputs that have different relative phase changes in opposite directions. An optical non-reciprocal phase shifter is obtained.

According to a further feature of the invention, for the selected wavelength, in the first propagation direction characterized in that the output light is effectively transmitted and in the opposite direction the output light is effectively attenuated. An optical isolator having a characteristic non-reciprocal phase shifter is obtained.

Yet another feature of the invention provides that substantially half of the incident light is transmitted between the first and second optical paths. a device for propagating through each of the optical fibers, and at least the first optical path comprises: a polarization plane rotation device that performs rotation depending on the propagation direction, and at least the second a second polarization plane changing device that rotates the optical path without depending on the propagation direction; ” has an optical path and a second optical path length difference, and the first optical path and the second optical path are different from each other. having a device for recombining the two optical paths and having a first wavelength propagating in a first direction; sufficient attenuation occurs for the light that propagates in the opposite second direction, while attenuating the first wavelength that propagates in the opposite second direction. virtually complete transmission occurs for the light that has the Virtually complete transmission occurs for light having two wavelengths, while in the opposite said second direction. configured to cause sufficient attenuation to the propagating light having the second wavelength; An optical bidirectional isolator is obtained.

According to still further features of the invention, at least one person for the non-reciprocal isolator a device for coupling the isolator to two terminals; is configured to output light having a first wavelength through the first output, and a second wavelength an optical circuit configured to output light having a length through a second output; data is obtained.

According to still further features of the invention, the signal propagating in the first direction has a first wavelength; Signals propagating in the direction of bending @2 wavelengths, and both signals propagating in the same optical fiber The device propagates through one or more wavelength-selective bidirectional isolators. A bidirectional fiber optic communication device is obtained, characterized in that it comprises:

According to still further features of the invention, at a first wavelength in a first direction and at a second opposite wavelength. amplifying a signal at a second wavelength of the direction; a device for inducing gain at two wavelengths, and a bidirectional wavelength-dependent separation device as described above. A signal of the first wavelength propagating in a first direction and a signal of the second wavelength propagating in the second direction. The signal is transmitted and a signal of the first wavelength propagating in the second direction; and a signal of the second wavelength propagating in the first direction. Wavelength signals are attenuated and Unfavorable feedback at the first wavelength and the second wavelength or virtually be deterred, An optical bidirectional amplifier configured as follows is obtained.

Yet another feature of the invention provides that substantially half of the incident light can be filtered, each with an arbitrary plane of polarization. a device for transmitting said light into two optical paths having a a device for ILT coupling the optical paths, and each of the optical paths has a plane of polarization of the plane-transmitted light. an output device in which the optical paths are in phase in a first direction of propagation; and that in the opposite direction the optical path is 180 optical system, characterized in that it has outputs with different degrees of phase and therefore does not transmit incident light; A typical isolator can be obtained.

Brief description of the drawing Some implementations of the present invention will be described with reference to the drawings.

Figure 1 is a schematic diagram of a prior art isolator.

FIG. 2 is a schematic diagram of yet another prior art isolator.

FIG. 3 is a schematic diagram of an optical circulator.

FIG. 4 is a diagram of a first technique for bidirectional separation in a wavelength branching propagation device.

FIG. 5 is a diagram of a second technique for bidirectional separation in a wavelength branching propagation device.

FIG. 6 is a conceptual diagram of a technique for bidirectional separation in a wavelength branching device.

7A and 7B are diagrams of interference in the apparatus of FIG. 10.

FIG. 8 is a diagram of one embodiment of the apparatus of FIG. 10.

'F, FIG. 9 is a diagram of another embodiment of the apparatus of FIG. 10;

1I OA and 10B are diagrams of preferred embodiments of non-reciprocal phase shifters.

Figure 1 is a diagram of an isolator without polarization plane dispersion.

FIG. 12 is a diagram of an isolator without balanced polarization plane dispersion.

Figure ff113 shows an integrated implementation of a circulator/isolator according to the invention. Example illustration.

FIG. 14 is a graph showing wavelength dependence in the experimental equipment.

FIG. 5 is a diagram of a preferred embodiment of the apparatus of FIG. 1O.

FIG. 16 is a schematic diagram of a bidirectional amplifier.

FIG. 17 is a schematic diagram of a fiber-embedded circulator according to the present invention.

FIG. 18 is a diagram of an embodiment of the apparatus of FIG. 17.

FIG. 9 is a diagram of a mote conversion circulator.

No. 20B is a molten Matsunototsu fabrication of a circulator/isolator according to the present invention; Diagram of Noda embodiment.

FIG. 21 is a diagram of a filtering isolator according to the present invention.

FIG. 22 is a diagram of a high separation device.

FIG. 23 is a diagram of a circuit network using a bidirectional amplifier.

FIG. 24 is a schematic diagram of a low polarization dispersion amplifier.

detailed description This feature of the invention is particularly suited for implementation in bidirectional networks. This method The principle of a propagation device designed using separation is shown in Figure 23. So, one propagation in the first direction is at the first wavelength, and the propagation in the second direction is at the second wavelength. It is carried out at the wavelength of One particular difficulty in this configuration is to perform wavelength selective separation. The idea is to create a simple isolator. If you create an isolator like this It is clear that the amplifier will be adequately isolated from reflections if it is possible to do so. Ru. That's because such reflections usually preserve the wavelength of the light. Therefore, when it encounters the isolator, it passes through the device.

Several schemes can be adopted to achieve the required termination.

A first embodiment of this type of isolator is shown in FIG. splitting the light into two wavelengths using a wavelength division multiplexer 34; , each wavelength is separated separately in each direction using isolators 32 and 33. This is done by separating and then recombining the light at 31. A little more fine An ingenious scheme is shown in FIG. It is configured using a multiplexer element 41.

This feature of the invention uses interference properties to perform the separation instead of relying on polarization dependence. , is based on a novel method. One immediate benefit from this is that the explanation All the examples presented are totally polarization independent and can separate and recombine polarized light. There is no need to do so. Some of the illustrated embodiments are single mode waveguide responses. Although the overall concept applies equally well to many isolators, can be used.

The general form of this feature of the invention is illustrated in FIG. enter position 1 One light beam is formed by beam splitter 51 using mirrors 54,55. The beam is divided into two optical paths. A 90 degree Faraday rotator 53 is in the fourth optical path. A pair of half-wavelength retardation plates 52 are arranged at a relative angle of 45 degrees in the second optical path. It is arranged with The pair of delay plates 52 adjust the polarization plane of incident light having an arbitrary polarization plane. Rotate by 90 degrees.

This can be shown by appropriate Jones matrix multiplication.

Here, additive interference can be reliably obtained when proceeding from optical path (1) to optical path (4). In order to achieve this, the optical path lengths of both arms are adjusted to be equal. Light enters end 4 In the case of opposite optical paths, the polarization of the two light beams would be opposite. it is, Is Faraday rotation independent of the direction of light travel, while birefringence rotation is the opposite? It is et al. This corresponds to a 180 degree phase change in the electric field vectors of the two light beams. However, subtractive interference may occur at the edges. Instead, the light exits through end 2. will form an isolator.

The created device is associated with the Matsuha-Zehnder interferometer. wavelength in separation It will be clear that dependencies are obtained. If the Matsuha-Zender interferometer If an optical path length difference is introduced between the two arms, proceeding from end 1 to end 4, There will only be certain wavelengths of light that are either interfering or additive. This is the end This will give the intensity of the light exiting the section 4 a sin'' dependence as a function of λ.

This is periodically proportional to the optical path length difference I/ΔI, and the remaining light goes back to end 3. .

There is a 180 degree phase difference between the light beams traveling from right to left, as shown in Figure 7A. The transmission curves at all ends 1 are similar to the transmission curves obtained at end 4 shown in FIG. 7B. would be complementary. In the case of forward propagation, the wavelength for additive interference at end 4 On the other hand, in the case of reverse propagation, additive interference would be obtained at end 4.

This is exactly the characteristic required for an isolator with wavelength dependence.

For example, by using an optical path difference of 0.12 mm, forward propagation at 1535 nm (corresponds to the first gain peak of the erbium-doped fiber amplifier), and its and reverse propagation at 1555 nm (the second phase of the erbium-doped fiber amplifier). The device can be configured such that the gain peak is on both wavelengths On the other hand, separation can be obtained.

The main issue to be solved is the stability of the device against external perturbations. be. Since it is an interference device, it has no resistance to thermally or mechanically induced optical path lengths. potentially extremely sensitive to fluctuations in thermal and mechanical stability Although it is possible to Neither is likely to have the stability required for field devices.

One solution is that the effect of thermal expansion affects all arms (with a very small optical path difference I/Δ1 The entire device is solid, considering the balance of the configuration of the arms so that they affect each other equally (with the exception of It is created from parts. This is illustrated in FIG. The incident light 62 is silver incident on the plating surface 63 and passing through the rotor 67 and half-wave plate 68, or It passes either through the rotator 64 or the half-wave plate 65, and finally becomes the output light 66. Ru. It will be clear that an isolator similar to that of FIG. 6 may be constructed. one arm Instead of a 90 degree Faraday rotation occurring in the first arm, a 45 degree Faraday rotation occurs in the first arm. Happens, and minus 45 counter-rotations in the second arm, and the first quarter in the first arm a quarter-wave plate is disposed in the second arm and a second quarter-wave plate is disposed in the second arm. I want to be noticed. The equivalence of this to the traditional construct is that the Jones matrix This can be illustrated again by However, there are many waves specifically related to optical communications. Creating a 50% beam split cube that is polarization insensitive in length is extremely difficult.

The second solution is to physically divide the light beam between the upper and lower halves, as shown in Figure 9. split it in half and use the same rotor and birefringent plate as before. . Lens 73 converts the incident light into a parallel light beam 75, and lens 71 converts the incident light into a parallel light beam 75. beam 75 and projects the light onto a set of mirrors 70. Here, this device is supposed to act as an isolator, or is there any interference at all? It's not even clear if it's supposed to happen. In fact, this device is a solid isolator. It will no longer work. Interference or separation occurs between the input cuff 4 and the output cuff 4. Only when both Fiber 2 are single mode fibers. This is the fiber model. This is due to the quantum nature of the code.

Qualitative and theoretical understanding by considering this device as a black box Can you get it? With this device, for photons propagating in the forward direction, equal Two optical paths with high probability and the same phase are obtained. At a certain position in the second fiber The expected value that a photon reaches is (possible different wave functions and the probability of that wave function) It is the sum of the product of In the forward direction, the wave function for a photon of a given wavelength is will be in the same phase. Then, the normalized expected value is l (the photon reaches There is a probability of 10096). For the same wavelength and opposite directions, the wave function has the opposite sign. It would be the number. Therefore, the probability of a photon arriving will be zero.

The above consideration is easy to prove using the formulas of Fourier optics. assumed The cross-shaped mode is converted into a cross-shaped beam in Fourier space by the lens. It will be done. If there is no phase delay, the second lens converts the light beam back to its original shape. and this converted light beam is transferred to the second fiber in the fundamental mode. sufficiently excite the Using the terminology of quantum mechanics, the overlap between the mode and the excitation light is The integral is! It is. 100% transmission is obtained. If the upper half of the beam is only π If subject to a phase delay, then this means that the upper half of the Fourier transform is −1 is equivalent to multiplying by . When we perform the Fourier transform corresponding to the second lens, , an odd function can be obtained. The overlap integral of an odd function and an even function is necessarily zero.

Here it is clear what is happening to photons being lost from the device.

These photons are simply trying to excite higher-order modes, and this higher-order mode The next mode is cut off and cannot propagate through the fiber.

These photons are lost very quickly into the fiber cladding.

This principle was demonstrated by constructing a very simple interferometer in the laboratory. this It was found that the Interference 51 is more stable as it flies. The optical flat plate consists of two single modules. inserted into the beam expander between the lead fibers to occupy the upper half of the beam. It was. The reception as a function of wavelength corresponds to two optical paths that are in phase and out of phase. There is a clear modulation in the ejected light. This is illustrated in FIG.

This provides yet another arrangement for bidirectional isolation. In this case, the expansion The enlarged beams are never physically separated. 90 degree Faraday 76 rotor and a pair of intersecting half-wave plates 74, one side surface of which is polished and a pair of crossed half-wave plates 74. It is created by joining. This composite element is shown in Figure 15. so that it occupies exactly half of the beam. faraday By providing slightly different optical paths between the rotor and the birefringent element, the optical path difference can be reduced. It is possible to achieve. A conceptually equivalent device to this device is shown in Figure 9. Ru. By slightly changing the angle at which the element is inserted into the beam, the propagation can be modified. Can be tuned to a precise wavelength. The thickness of this composite element is comparable to that of the state-of-the-art Faraday In the case of a rotor, it need not be much larger than 500 μm. Good beam expansion optics For devices, the insertion loss is negligible (<0.5 dB), and the optical path difference Since only crystals of small length ~Imm) give rise to Ru.

One drawback of the embodiment described above is that each half of the beam to be separated In order to function, the construction of the non-reciprocal phase shifter uses different materials.

Therefore, the thermal expansion coefficient and thermal refractive index coefficient of each half body will be different. Therefore, this device will be subject to temperature changes. Therefore, separation is the largest wave. The length will vary.

Figures 10A and 10B illustrate a preferred stable design of a non-reciprocal transfer element. This is a drawing.

This embodiment has a 45 degree Faraday rotator 101 on both halves and half-wave plates 100 and 102 are used. In the first half, the half-wave plate 100 is On the left side of the Faraday rotator +01, and in the second half, the half-wave plate 102 is It is located on the right side of Faraday rotator 101. The optical axis of the second half-wave plate 102 is the first half-wave plate 102. It is oriented at 45 degrees with respect to the optical axis of the long plate +00.

In order to understand the operation of this device, we need to use a device with no wavelength dependence for vertically polarized + + Consider a path of light traveling from left to right with 04. In the upper half of the beam, the light is passes through the fast axis of the half-wave plate 100 and then passes through the Faraday rotator +01. , rotates the plane of polarization 45 degrees clockwise. The light in the lower half of the beam is first Faraday round The plane of polarization rotates 45 degrees clockwise through the trochanter 101, and the plane of polarization rotates through the half-wave plate 1. It is aligned with the high speed axis of 02. When these two beams are recombined, they are It will probably be in phase. Similarly, for light with horizontal polarization +05, the upper half and the lower half The light that passes through both halves passes through the slow axis of the half-wave plates 100 and +02, and Once upon a time, they would be in the same phase. Light traveling from right to left is on the vertical axis in the upper half It rotates 45 degrees clockwise relative to the target and first enters the Faraday rotator 101, where it Polarized plane or water 51! It rotates axially and then passes through the slow axis of the half-wave plate 100. from the right The light traveling to the left is rotated 45 degrees clockwise with respect to the vertical axis, and the lower half is rotated 45 degrees clockwise with respect to the vertical axis. 102, then passes through the Faraday rotator +01, and the plane of polarization becomes water. It will be in the flat axis direction. The upper beam goes through the fast axis and the lower beam goes through the low As it travels through the fast axis, there is a 180 degree relative position between the upper and lower halves of the beam. There will be a difference. In the forward direction, additive interference occurs as the light recombines and In the opposite direction, when the light recombines there will be subtractive interference and therefore attenuation.

This is the basis of non-propagation, that is, separation. As you will soon see, this means It can be easily expanded and applied to circulators.

The isolator explained in Figure 10 has a one-wavelength difference between the two polarization states in the forward direction. It has a very small (but limited) polarization dispersion. This is one polarization power plane wavelength through the fast axis of the plate (upper and lower halves), and the other polarization power plane wavelength This is because it travels through the slow axis of the plate. The resulting polarization dispersion is 1. 5 For μm light, it is equal to 5 fs. This value is based on the best commercially available isolators. We designed an isolator with essentially zero polarization dispersion power, which is much smaller than the value of It is possible to do so. This means that the forward axis is equivalent to a fast axis pass and a slow axis pass. This is executed by creating one transport path. Figure 11 shows that this This is a drawing showing how this can be achieved. The upper half has fast axis, f-axis for vertical polarization. Faraday rotor: low speed axis for horizontal polarization Low speed axis, Faraday rotor, high speed axis It consists of

The lower half has an optical path length equivalent to the fast axis and the Faraday rotator ten to the slow axis for both polarizations. configured.

There is no inherent polarization dispersion.

Figure 12 is equivalent to Figure 11 except that the design is again fully balanced.

As shown in Figure 9, J IL-pure optical circulators can be easily implemented. of isolator If in the non-propagating direction () [the light to be divided is asymmetric with respect to the axis of the interface, but Therefore, it is not possible to excite the fundamental mode in the Hua-Moat fiber. However , the first higher-order moat of the multi-moat fiber 110 can have the same symmetry. can be excited. By using a fiber that maintains this higher-order mode, and then create a coupler 115 that couples this higher order mode to the second fiber. By doing so, it is possible to perform the function of a 3-terminal or 4-terminal circulator. can.

Single mode fiber +16 is coupled to multimode fibers +18, +10 14.115. The lenses 111, +13 and phase shifter book 2 are as described above. Forms a beam expanding isolator. Such a coupler can be used for higher orders of correct symmetry. Light can be coupled from the moat into the fundamental mode of a single mode fiber.

In this case, the propagation coefficients are matched in the coupling region. Fusion bonding method or polishing bonding method Either can be used. At the interface of the crystal in the expanded parallel beam, the height The second mode 1 - non-optimal excitation activity is achieved to fill the remaining amount lost for this device. child This is because the light beam has an interface that transitions from a near-field image to a far-field image. It can be a government office. By concentrating the light between the lenses and non-reciprocal transfer This is achieved by placing the phase crystal in the appropriate position.

In Figure 3, in this example, the Matsuha-Zehnder waveguide is an integrated optical Created with academic equipment. These devices are commercially available. Matsuha Tsuenda 113 A groove is created passing through both arms of the Half of the physical strength of an ITI person. As a result, the light from the first arm passes through the first half. , and the light from the second arm passes through the second half. Non-guided propagation over this region 1, use beam expansion techniques if necessary to reduce the loss of tl due to be able to. As usual, a magnetic field must be applied to the Faraday rotator . This device is commonly used to combine it with an integrated splitter. It can be combined with other integrated optical devices in the formula.

Figure 20 shows another pine needle with two fibers using fused coupler technology. 1 is a drawing of a Zehnder embodiment. The illustrated embodiment is based on the refraction of the cladding of the fiber. Two fibers 115 are inserted into a glass tube 114 with a refractive index smaller than the , and this tube is tapered across two adjacent regions 113, and has two adjacent regions 113. A 5050 coupler is formed. The surrounding crushed glass tube +14 allows the specified With the fiber +15 held firmly in position, the non-reciprocal phase shift element 112 This device can be cut and polished before being placed between the fiber waveguides. Ru. Alternatively, as for the integrated optical device shown in FIG. 6 can be used. This example provides low-loss coupling of light through a non-reciprocal phase shifter. It has the potential to be ill. By enlarging the fundamental mode, the diffraction effect can be reduced. and propagation through the non-guided region can be achieved with low 714 losses. Bee The beam expansion can be achieved by using a fiber with a tapered fF region or by using a fiber with a core With diffusion technology, it is possible to make it to J1.

Single polarization fiber embedded isolators have been disclosed in the scientific literature. Kereto However, the applications of single polarization devices are extremely limited. By the device shown in Figure 15 , an isolator that is not sensitive to polarization is obtained. The light from a single mode fiber is It is expanded by a lens 73 to become an expanded beam. The non-reciprocal phase shifter 112 A Faraday rotator 76 in one half of the system 75 and a pair of half-waves in the other half. It is formed as a long plate 77. Lens 71 propagates light into fiber 72 .

It will be seen that this principle of operation is similar to that of the apparatus of FIG.

These could potentially be made into separate connectors. like this The device can be either wavelength independent or wavelength sensitive. can.

A split beam isolator (or standard eye for that problem) Another feature that can be incorporated into the Solator is the Zub1 Lunoto Beam Technology. This is a filter effect using . Non-birefringent inverse element, e.g. non-birefringent wavelength By separating the beams using plate 117, a sinusoidal filter is created with different optical path lengths on each side. A data effect can be applied. This is shown in FIG. Amplifier response This is particularly useful for equalizing the gain over a fixed bandwidth in applications. It is for use. To combine this with the type of isolator described above, the reverse The interface of the filter acting element must be perpendicular to the interface of the non-reciprocal phase shifter 112. stomach. By separating the beams using a ratio other than 5050, the desired degree of excitation can be achieved. Can you get it?

To obtain properties of a higher degree of separation or properties that are more independent of temperature Additionally, the ability to cascade these devices is extremely simple. The device interfaces are mutually The two non-reciprocal phase shifters 112, 122 are They can also be cascaded within the same beam expander. This is shown in Figure 22. It is. Constant tuning of the device characteristics also allows for slight variations from 90 degree relative orientation. This can be achieved by To increase instrument peak separation and separation width , two identical devices can be cascaded. or with slightly different center wavelengths. 2H devices can be cascaded to obtain even wider separation bandwidths.

Peak separation wavelength tuning The wavelength of peak separation can be tuned to be different from the wavelength of 45 degree Faraday rotation. is for (r) at the wavelength of the required peak separation, a half-wave plate By choosing the relative angle between the optical axes of to be equal to the Faraday rotation angle, This can be achieved according to the invention. This property is suitable for wideband separation. can be combined with the above characteristics to be or vice versa for well separated wavelengths. Can be combined to achieve direction.

Equipment synchronization One important practical issue, separate from the wavelength of peak separation, is the required single or is the tuning of the instrument to ensure that maximum extinction occurs at multiple wavelengths. It is. The light from each half of the non-reciprocal phase element is to ensure that they are exactly in phase at one or more wavelengths This is achieved by: This is most easily achieved by changing the angle of the crystal. The relative phase between each half can be tuned. Optical path length of both halves If the two halves have different angular orientations, rotate the entire device. This can be achieved by: Split beam implementation case If this rotation occurs in one plane, such that the interface of the crystal remains perpendicular to the beam must be done.

Other tuning mechanisms are also possible. in the Fourier plane (i.e. in the expanded beam) ) is equivalent to a lateral displacement perpendicular to the interface in the image plane. It is worth it. Therefore, another method is to tune the fiber to It is a lateral displacement from the true image position. This tuning mechanism has a small loss Useful for degree or fine tuning.

In contrast to the temperature-independent broadband case of phase change due to material equilibrium, the equilibrium design is non-reciprocal. Although each half of the antiphase shifter has exactly the same material, the bidirectional design b] requires additional optical path length and therefore reduces the thermal expansion of the unbalanced part. Due to the temperature dependence of the refractive index, there is potentially some degree of temperature dependence on the phase. It should be noted that At least two methods can be adopted.

One method is to use a material with very small temperature dependence for the phase shifter. Ru. Another scheme uses two in each half of the non-reciprocal transfer device to obtain optical path difference. using different materials. These materials have small optical path lengths or large thermal coefficients. They are selected to have slightly different thermal coefficients, so that the number of this method to make the relative phase virtually constant over a wide temperature range. be able to.

Fiber-embedded optical circulator Figure 17 shows beam separation or optical coupling. The apparatus described above, such as that of FIG. This is a drawing of a circulator using the principle of the device. 90 degree faraday rotator 88 is embedded in one arm of the Matsuha Zenda, and 90 in the other arm. A degree birefringence rotator 88 is embedded, thereby (or as described above) and other combinations) form a circulator.

One method of manufacturing this device and keeping the arm length to an absolute minimum is the first This is explained in Figure 8. V-shape of fused silica to align each fiber Grooves 90,92 are used and a 90 degree Faraday rotator 93 is aligned along the fused silica. is embedded in one fiber 130, and the plane of polarization is rotated by 90 degrees. A refractor plate 94 is embedded within the pond fiber +31. Next, use a quartz V-shaped groove. and polish continuously until 100 percent bond is achieved in the forward direction. creates a polished coupler. This must be done before and after the rotating equipment. This corresponds to 50% binding. This device is identical in operation to the device shown in Figure 17. However, it is extremely small and resistant to the environment. This device is It will work as a controller. And mass production would be possible. Suheh Since all circulators are also isolators, this device is of course 2 is another embodiment of an isolator. Place the fiber at the location where the crystal embedding will take place. Is it necessary to slightly embed it in the quartz or is this practical for the operation of the device? It will not have any negative impact.

FIG. 24 is a diagram of an amplifier arrangement using the isolator of the present invention. This structure Adults have a small polarization dispersion. Pump source 131 and input signal 142 input into the splitting multiplexer 135 and into the low birefringence erbium-doped fiber 13. 2 and polarized light (e.g. as described in Figures 1+ and 12) incident on the dispersion isolator 138. The signal is then transferred to the low-birefringence erbium-doped film. passes through fiber +34 and wavelength division multiplexer +36 and then to output 143 . Pump source 137 drives the erbium fiber amplifier.

A format that allows bidirectional communication in a single fiber using the same amplifier for both wavelengths. A bidirectional amplifier is shown in FIG. Its configuration is the same as that in Figure 24. However, a bidirectional wavelength-dependent isolator 13 (e.g., as described in FIG. 6) 3 is included. The isolator 133 consists of two erbium-doped fibers. It is placed between the amplifiers 23132 and +34. At 140, the signal at λ1 is input , and the signal of λ2 is the output. 141, the signal of λ2 is the input , and No. 13 of λ1 is the output. At different frequencies, e.g. At a large input λ, the signal corresponding to the permissible direction is suppressed. Therefore, the increase True bidirectional amplifier with no undesirable feedback to cause problems with amplifiers As such, a truly bidirectional device is possible.

It will be readily apparent that various modifications and additions can be made within the scope of the invention. There will be.

Engraving (no changes to the content) rotor Polarizer Polarizer Transmittance A rate Transmittance half wave plate 45° full rotation Tips? + Mahe 2 axes half wave plate Vertical axis 1:l1iiill 1II II+ to balance the optical path length optical flat plate horizontal axis 1.466 1j36 1.586 5nm 10nm/dlv Copy and translation of amendment) Submission (Patent Act @ Article 184-8, October 1994) 3 day V ’4=’r　；TōI″J″′long′self゛゛　1　, 41i,, i Application indication P CT/AU931001462 Name of IUI issued Improvement of optical phase shifter 31'i applicant Name (Name) Telstra Corporation Limited Name (66f3 9) N-Hen Osa 4th Transfer IF (No change in content) The signal of the first wavelength propagating in the first direction and the signal of the first wavelength propagating in the second direction. The signal of the second wavelength is transmitted, and 13 of the first wavelength propagating in the second direction and before propagating in the first direction. 18 of the second wavelength is attenuated, and Unwanted feedback at said first length and at said second wavelength is effectively suppressed. be stopped, Optical bidirectional amplifier.

(I2) Virtually half of the incident light is sent to two optical paths, each with an arbitrary plane of polarization. a device for transmitting light, and a device for recombining the optical paths to produce an output. , and each of the optical paths includes a device for changing the plane of polarization of the transmitted light, and In the first direction of propagation, the optical path has an output that is in phase and therefore transmits the incident light. and in the opposite direction the optical path has outputs with a 180 degree phase difference, thus An optical isolator characterized by not transmitting incident light.

(13) It has a non-reciprocal phase shifter and is in the first propagation direction for the encountered wavelength. effectively transmitting the output light in the opposite direction and effectively attenuating the output light in the opposite direction. An optical isolator characterized by:

(I4) It has a device that expands incident light with an arbitrary plane of polarization into a light beam, and a device for refocusing the light to produce an output; and a device in the middle of the beam. a non-reciprocal phase shifter having at least a first portion and a second portion; the third section has a polarization plane rotation device having a rotation that depends on the propagation direction; , at least a second device for changing the plane of polarization that does not depend on the propagation direction rγ. characterized in that the second optical path exists, and in the first direction of propagation of the incident light. The output is effectively attenuated and in the opposite direction the output is effectively transparent to the incident light. constructed of optical isolators.

Procedural amendment (voluntary) Name Telstra Corporate Limited Specification, Scope of Claims and engraving of the abstract title translation (no change in content) procedural amendment (voluntary)

Claims (14)

[Claims] (1) at least one first polarization whose rotation direction of the polarization plane depends on the propagation direction of the transmitted light; a light plane rotation device; and at least one for changing the plane of polarization independent of the propagation direction of transmitted light. and a second device for changing the polarization plane of the phase shifter, and the polarization plane can be changed from both ends of the phase shifter. Virtually half of all light propagating through the first polarization plane rotation device and polarization light propagating through each of said second devices for changing the light plane; Non-reciprocal phase shifter. (2) the incident light propagates through the first optical path and the second optical path and at the output the said light a device for recombining optical paths, each of said optical paths having an arbitrary plane of polarization; each has a first device and a second device for changing the polarization plane of the emitted light, and at least one of said devices for further rotation makes a first rotation relative to a first propagation direction; and a second rotation relative to a second propagation direction, and of said device for modification. the other or one makes a change independent of the direction of propagation, and a first relative position between the optical paths; a phase change occurs for light propagating in a first direction, and a second relative phase change occurs between the optical paths; an optical non-reciprocal phase shift configured such that the change occurs for light propagating in a second direction; vessel. (3) the incident light propagates through the first optical path and the second optical path and at the output the said light a device for recombining optical paths, and wherein the first optical path is in a first propagation direction. A first polarization plane rotation device that rotates depending on the direction of polarization and a polarization plane that rotates independently of the propagation direction. a second device for changing the surface, and the second optical path is in the first propagation direction. A third device for changing the plane of polarization and the direction of propagation, which changes the plane of polarization independently of the direction of propagation. and a fourth polarization plane device with a rotation dependent on propagates through each of the first optical path and the second optical path, and the phase of the output light is Optical non-reciprocal phase shifter in which the phase change depends on the direction of propagation of the incident light. (4) In the optical non-reciprocal phase shifter according to item 3, the first polarization plane rotation device and and the third polarization plane rotation device is arranged in both optical paths. The optical non-reciprocal phase shifter obtained by the following method. (5) Virtually half of the incident light passes through two optical paths, each with an arbitrary plane of polarization. a device for propagating through and recombining said optical paths at an output; each having a device for changing the plane of polarization of the propagating light, and in the first propagation direction; the optical path has an output having a first relative phase change in the opposite direction; an optical non-reciprocal phase shifter, wherein the optical path has an output having a relative phase change of (6) propagating virtually half of the incident light through each of the first and second optical paths; and a polarization device in which at least the first optical path rotates depending on the propagation direction. an optical surface rotation device, and at least the second optical path is changed without depending on the propagation direction. a second device for changing the plane of polarization, and the first optical path and the second optical path a device for recombining the first optical path and the second optical path, the paths having an optical path length difference; has, and Complete attenuation occurs for light with the first wavelength propagating in the first direction, while substantially complete transmission occurs for light having said first wavelength propagating in a second direction; and virtually complete transmission occurs for light having a second wavelength propagating in the first direction. On the other hand, the light having the second wavelength propagating in the opposite second direction is substantially completely Optical bi-directional isolator configured to provide maximum attenuation. (7) has at least one input to the isolator described in paragraph 13, and having a device for coupling the isolator to the two terminals and transmitting in one direction. configured such that light propagating through the isolator and one terminal; and allows light propagating in other directions to propagate through the other terminal and the isolator. An optical circulator configured as follows. (8) has at least one input to the isolator described in paragraph 13, and a device for coupling the isolator to the two terminals, and has a first mode. The light is configured such that the light is output through the first terminal, and has a second mode. an optical circulator configured to output through a second terminal. (9) A signal propagating in the first direction has the first wavelength and a signal propagating in the other direction has a second wavelength, and both signals propagate in the same optical fiber, and one or or a plurality of wavelength-selective bidirectional isolators. Fiber communication equipment. (10) In the bidirectional optical fiber communication device according to item 9, the isolator 13. The bidirectional optical fiber communication device which is the isolator according to item 12. (11) At a first wavelength in a first direction and at a second wavelength in an opposite second direction. amplifying a signal and inducing a gain at the first wavelength and the second wavelength; and a bidirectional wavelength dependent separation device propagating in the first direction. A signal of a first wavelength and a signal of the second wavelength propagating in the second direction are transmitted, and a signal of the first wavelength propagating in the second direction; and a signal of the second wavelength propagating in the first direction. wavelength signal is attenuated and Unfavorable feedback at the first wavelength and the second wavelength is effectively be deterred, Optical bidirectional amplifier. (12) Transmit virtually half of the incident light into two optical paths, each with an arbitrary plane of polarization. and a device for recombining the optical paths to produce an output; and each of the optical paths has a device for changing the polarization plane of the transmitted light, and in a first direction, the optical paths have outputs that are in phase and thus transmit the incident light. and that in the opposite direction the optical path has outputs that are 180 degrees out of phase; An optical isolator characterized by not transmitting incident light. (13) having a non-reciprocal phase shifter and in the first propagation direction for the selected wavelength; Effective transmission of output light and effective attenuation of output light in the opposite direction An optical isolator featuring: (14) A device that collimates light into a light beam, and a part of the light passes through each element. Multiple optical elements are placed in the middle of the light beam so that it propagates, and the light is focused. A device for producing an interference effect, comprising a device for producing an interference effect.