JP2018510375A - Optical fiber coupler - Google Patents

Abstract

A fiber optic coupler according to the present invention comprising a multi-core optical fiber having an insulated core, wherein the core insulation is considered to be a refractive index reduction zone in the vicinity of the core, bonded to N output optical fibers Including at least one input optical fiber joined to at least an N-core multicore optical fiber having an insulated core, wherein the core insulation is reduced by reducing the size of the refractive index reduction zone in the vicinity of the core A fiber optic coupler that is reduced in at least one of the parts. [Selection] Figure 2

Description

  The subject of the present invention is a fiber optic coupler using a multi-core optical fiber with a fine structure.

  A power coupler is one of the basic components used in communication lines based on the use of optical fibers. To develop higher data transmission densities, the telecommunications market must take into account the requirements of data recipients with a focus on increasing data transmission density, improving functionality and reducing the cost of introducing new systems. . The purpose of a fiber optic coupler is to transmit power from one or more input optical fibers to one or more output optical fibers. The coupler can be implemented with any input / output configuration. The most common types of couplers include x-type couplers (2 inputs, 2 outputs) and y-type couplers (1 input and 2 outputs / 2 inputs and 1 output). There are both symmetric and asymmetric versions of such couplers. However, market demand determined that it would be necessary to produce a coupler with a higher number of channels. If desired, the coupler can have any number of inputs and outputs, whereas the main constraint is the coupler manufacturing capability. In an extreme example, if the coupler has fewer inputs than the outputs (especially if the coupler has one input and N outputs), the coupler becomes a power splitter. If there are N inputs and one output, the coupler becomes an optical signal combiner.

  To ensure full deployment of access networks defined as state-of-the-art access networks, especially FFTx networks (fibers drawn into x, eg FTTH-fibers drawn into the home), properly integrated power splitters and combiners is necessary.

  The FTTx network is usually constructed with PON (passive optical network) technology. There are point-to-multipoint networks that run in a logical star topology. The physical topology depends primarily on the distribution of subscribers: for single-family homes, the most common topology is a bus network, whereas for multi-family homes the most common solution is a tree. Topology. In any case, the central point is composed of an optical coupler that divides the signal from a distribution device, that is, an OLT (optical line termination device) to a network terminal with a recipient, a so-called ONT (optical network terminal device).

  The latest commercially available signal coupling elements utilized in telecommunications are generally manufactured using two technologies: fiber optic fusion (FBT-Bionical taper) and planar technology (PLC-planar lightwave circuit). In the case of bus network technology, the optical coupler utilized is usually implemented in FBT technology, and in the case of a tree network topology that requires a large number of output ports, the main solution utilized is a PLC coupler. It is.

  An FBT coupler is formed by placing two optical fibers adjacent to each other, then fusing them together and tapering them to create a single waveguide. With this structure, appropriately close cores can no longer be treated as separate communication channels. The signal entering one of the coupler arms passes to the taper area where the optical fiber size is significantly reduced, so that the core loses its ability to transmit light, so that the light is conducted by the entire glass surface and air Plays the role of cladding. When the tapered optical fiber is expanded, the core whose diameter increases also restores its light guiding ability. In such an arrangement, Maxwell's equations are solved for the entire structure, resulting in a so-called super mode that propagates through some or all of the cores simultaneously. Depending on the configuration, a power combiner or splitter can be constructed using light propagation in such a structure.

  A coupler manufacturing process through fusing by FBT technology is described in US Pat. No. 4,550,974, which describes the aforementioned coupler and its manufacturing method. Although the coupler presented here is a symmetric 2x2 coupler, it is also possible to produce asymmetric couplers, ie couplers with non-uniform power splitting. Such a coupler can operate in a 1 × 2 power splitter configuration if only one of the inputs is used. Its features are high resistance to external network condition changes, low insertion loss, and minimal retroreflection. One disadvantage of such couplers is that the maximum number of ports is four, and it is difficult to achieve uniform power division when there are more ports.

  In contrast to FBT, PLC planar technology has a larger number of input ports (4 to 128), which ensures a small size of the product itself, as well as a high operational stability over the entire spectral range of 1260 to 1650 nm. Can be manufactured. Such a structure is particularly used for integrated optical elements. A feature of a device having such a structure is that the loss is relatively large because mode conversion needs to be performed, and the internal loss is large, so that the entire loss reaches several decibels. In addition, techniques for assembling and connecting integrated optics and optical fibers require sophisticated and costly methods. The structure of the PLC coupler and its manufacturing method are described in particular in the patent literature, US Pat. No. 5,745,619 and US patent application 200301289A1.

  The basic parameters of currently used optical couplers are a major obstacle to the widespread use of access networks, particularly access networks defined as FTT networks based on the use of optical fibers used in all transmission stages. Accordingly, the object of the invention consisting of a fiber optic coupler that utilizes a finely structured multi-core optical fiber, particularly used as a power combiner and splitter, is to develop a device that serves as an element that ensures optimum power for any number of channels. Was that.

  On the other hand, the manufacturing technology that constitutes the essence of this patent presupposes the production of couplers from optical fibers that are more advantageous compared to planar technologies that are difficult to integrate into optical fiber based telecommunications systems. Depending on the manufacturing technology used, the device according to the invention keeps the losses low and ensures the necessary power split. Two criteria-specific power splits, and low losses during such splits, are key points in common utility. The developed all-fiber optical coupler makes it possible to reduce the optical power loss at the time of division to less than 0.5 dB, and theoretically, the loss can be close to zero. In addition, the devices described above can be used in a wide range of temperatures. An essential advantage of the present invention is that it can operate in any configuration, i.e., both a power splitter and a combiner, and an MxM coupler. In addition, being operable as a splitter / combiner / coupler, the device can be used as an optical switch.

  With the invention of photonic crystal fibers, also called microstructured fibers, the possibility of mode shaping in optical fibers has greatly expanded. In the case of microstructured fibers, the differential geometry (geometric difference) that involves the manipulation of the placement and properties of structural vacancies allows the inventors to generate fiber properties that could not be achieved using conventional optical fibers. can do. These properties include, for example, single mode operation over a very broad spectral range, high birefringence, high pressure sensitivity, stretch and many other properties. The effect of vacancies on the mode characteristics is negligible for light propagation that is not affected by external factors, but additional external factors can significantly increase fiber performance. Such an application can be, for example, a low bend loss fiber that includes a core whose optical fiber is surrounded by holes. Such an optical fiber is presented in a paper entitled “Low Bending Loss Single Mode Hole Assisted Fiber” published by Toshiki Taro et al. Published in SEI Technical Review 75 (2012). The advantages of this type of fiber become apparent when bent-in the case of optical fibers whose core is not surrounded by holes, bending results in considerable losses. In the case of hole-assisted insulation, there is a possibility of “mode outflow”, and the refractive index pitch of the large structure (the hole can be filled with various substances, but the refractive index of the hole region is the refractive index of air. Mode power radiation to the cladding is actually impossible. Therefore, the presence of holes does not affect the characteristics such as dispersion and attenuation because they are relatively separated from the core, but may affect the characteristics of propagation due to external factors. .

  Microstructured optical fiber vacancies can also be used to construct multi-core optical fibers without much involvement in propagation (a significant contribution is seen in the case of LMA-8 optical fibers). Due to the holes around the core, power propagation between specific cores is virtually eliminated-so-called crosstalk phenomenon does not occur. Furthermore, the holes can insulate the cores, meaning that the propagation of power within each core is substantially independent. Cores can also be surrounded by holes so that modes cannot be assigned to specific cores—such cores are called “coupled” cores, and supermodes propagate through the structure. Whether it is an insulated core or a bonded core depends on the material of the structure and the geometric parameters. In most cases, reducing the holes and bridging the holes closer will facilitate supermode propagation and thus power transfer between the cores.

  Microstructured optical fibers are widely available because their properties can be used by modifying their parameters, such as hole crushing, fiber tapering, hole filling, and the like. Therefore, it is also possible to change the propagation state after manufacturing the optical fiber.

  While hole destruction techniques are well known, the controlled use of this phenomenon has not yet been developed to achieve optical fiber coupling between the cores of certain multicore optical fibers.

  For example, US Pat. No. 6,663,234 describes the possibility of processing optical fibers by heating and tapering to obtain couplers based on photonic crystal fibers. Only single-core photonic crystal fibers are considered. The core collapse phenomenon is described as “weakening and destruction of the differential refractive index between the cladding and the core”. Furthermore, the birefringence of the optical fiber can be modified using controlled differentiation of the hole size and changing the diameter of the optical fiber.

  Hole breakage in photonic crystal fibers can also be used to connect microstructured optical fibers. The void destruction phenomenon has been regarded as a problem because it causes connection loss. This phenomenon can be exploited (eg, by gradual vacancy destruction) or eliminated. However, in most cases, the connection technology is considered for single-core photonic crystal fibers.

  For example, in the patent document, US Patent Application No. 20080037939, the inventors have tapered a single-core photonic crystal fiber that uses gradual vacancy destruction to reduce junction loss (connection loss). Presents.

  On the other hand, Japanese Patent Application No. 20060067632 discloses a single-core photonic crystal characterized in that, in order to minimize loss as much as possible, the connection execution method focuses on as few vacancies as possible and the core is small. The fiber connection method is presented.

  A method for connecting single-core photonic crystal fibers is also described in US Pat. No. 7,609,928 B2, where it is clearly stated that hole breakage is the cause of the loss.

  The use of hole crushing in the processing (connection, tapering, etc.) of a microstructured multi-core optical fiber can be used as a desirable phenomenon when constructing various types of sensors.

  For example, Patent Application No. 20090052852 presents a hole collapse method at the taper of a single core microstructured optical fiber. The invention is aimed at the complete collapse of holes that can interfere with each other by their mode (implemented in the core and cladding). In this way, a specific Mach-Zehnder interferometer is formed.

  A similar solution is described in the patent document, EP 19396659 B1, where the connection regions are fused and the clad mode and the core mode are implemented with two interferometers.

  Furthermore, modern telecommunications networks based on standard single-mode single-core optical fibers will soon become insufficient due to limited capacity. One strategy to solve this problem is mode division multiplexing, which uses a fumode optical fiber for transmission and each mode is used as an independent transmission channel. In order to be able to build a transmission network based on a fumode optical fiber, special components for multiplexing (multiplexing) and demultiplexing (demultiplexing) modes are required. Multiplexed mode combines signals from N standard single-mode fibers and introduces them into the multimode fiber (fu mode) as N independent channels. For this purpose, signal conversion from a standard single mode fiber to a specific mode is performed first, and then all channels are placed in a fu mode fiber. During demultiplexing, an inverse process is performed in which the N modes of the fumode fiber, which are several (N) independent channels, are split into N outputs. Therefore, there is a need for a device that can multiplex and demultiplex channels within a fumode optical fiber. In addition, it is necessary for this type of device to be characterized by low loss and high mode selectability.

  One selective mode excitation method uses a phase plate, or SLM. In either case, the light beam (usually the fundamental mode) strikes a transparent element having a predetermined refractive index profile that results in a phase structure—resulting in a specific higher order mode at a distance from the back of the plate. Similarly, an SLM that introduces an appropriate phase delay added can be used. When using an SLM, the phase delay can be programmed, resulting in an arbitrarily shaped higher order mode, so the SLM is very versatile in use. Both of these methods use bulk optics at the light beam input and output of the fumode fiber. As a result, unfortunately the size of this type of device, which often consists of several elements, increases. At the same time, using a device with high precision increases the price. Although this method seems to be the simplest, it involves losses. R. Ryf et al., “Mode Division Multiplexing> 96 Km Using Coherent 6 × 6 MIMO Processing” (2012, Lightwave Technol. Journal 30) describes multiplexing using fumode multiplexing of transmission over six independent channels. Presenting the transmission. The achieved transmission rate was 640 Gb / s over a distance of 96 Km and the loss was less than 1.2 dB. Also shown is a signal transmission system with a fumode optical fiber in which the element that shapes the beam into the desired mode is an SLM. In fiber optic networks, the use of bulk optics leads to introductory losses that are inevitably associated with transmission from the bulk optics to the optical fiber.

  Another method called “photonic lantern” is based on the tapering of several single core fibers with the required parameters. These parameters (core size, core refractive index) are generally different until the core stops independent light guiding, resulting in reduced refractive index and glass outer capillaries that serve as fiber cladding. Is formed. A specific mode can be obtained at the output by appropriately selecting the parameters of the single core fiber at the input. At the same time, it is possible to stimulate different modes at the output, depending on which input the single core fiber signal is introduced. The advantage of this method is that it uses very little loss and uses optical fiber technology (all-fiber type). However, the problem is to keep crosstalk between modes low. Currently, transmissions using this type of multiplexer have a high degree of coupling between the modes being multiplexed, so it is necessary to apply electronic signal processing during demultiplexing.

  It is also possible to use integrated optics for selective mode excitation. For example, there are converters based on long period fiber gratings. I. Giles et al., “Fiber LPG Mode Converter and Mode Selection for Multi-Mode SDM Technology” (2012, IEEE Photonic Technology Proceedings) describes such devices based on long-period fiber gratings and their test method concepts. Presents. Another way to use integrated optics is to use symmetric or asymmetric couplers. Another method for selective mode stimulation (excitation) is an asymmetric planar structure, a planar Y shape (Y junction). J. et al. D. Love, N.M. Riesen's paper "Single-number- and multimode Y junctions" (2012, Lightwave Technol. Journal 30, pages 309-309) describes this type of asymmetry used to stimulate higher order modes. Structural simulation results are presented.

  In particular, there is an example of a paper by Sung Hyok Chang et al., “Model using wavelength selection multiplexing based on a mode selective coupler and wavelength division multiplexing transmission” (2015, Opt. Express, No. 23). It uses fiber couplers for multiplexing and demultiplexing modes, and the solution relies on a cascade of conventional couplers. This solution does not include multi-core optical fibers or microstructured fibers, and using more than this multiplexing method is not easy to extend to more modes.

  Next, EP 2 336 913 relates to a multicore fiber for transmission using mode multiplexing without selective and particularly precise addressing modes. The modes in the fiber are coupled into groups and the core structure has no insulation. In the description of the invention, only the possibility of multiplexing and demultiplexing is mentioned, but the method of performing this operation is not disclosed. Indirectly in the description and drawings, it is concluded that this operation is performed by the planar phase plate, or the like. Thus, by using only fiber optics, multiplexing and demultiplexing are not included in the illustrated embodiment, and additional components that meet the purpose of the invention need to be used.

  Similarly, the solution EP 2706387 applies to an optical fiber for spatial multiplexing. In this embodiment, as described above, the multiplexing or demultiplexing phenomenon occurs only in the external element (outer optical fiber), and only the converted signal is introduced into the transmission-dedicated fiber.

  The elements that enable signal multiplexing are typically devices based on bulk optics, such as those disclosed in US Pat. No. 6,320,050 for bulk multiplexer designs. These types of solutions were expensive and inefficient, which was the starting point for the study of the present invention.

  On the other hand, U.S. Pat. No. 20133039627 relates to the use of a fiber with a coupled core for transmission based on mode multiplexing, but adds how the addressing mode is implemented. It is not disclosed what seems to be necessary based on the explanation of the experimental study.

  Next, U.S. Patent Application No. 2015188659 discloses a multiplexing and demultiplexing method using a ring resonator. This solution is characterized by enormous complexity and cannot simply be included in a fiber infrastructure given that its design is not pure fiber optics.

  Known solutions are notably characterized by tremendous complexity. Accordingly, the object of the present invention is to provide an element that eliminates the disadvantages of the prior art, which is problematic in controlling which mode is stimulated (synonymous with excitation and addressing), and by using it, a mode signal is obtained. To be able to run efficiently and independently. By using the present invention, it is possible to realize transmission using several modes (mode multiplexing) in one optical fiber. By using the present invention, it is also possible to realize an add-drop multiplexer. In addition, it was an object of the present invention to develop the entire structure with optical fiber technology that can avoid joining the planar / bulk optics and the optical fiber. According to the invention, it is possible to address modes, ie fundamental modes, higher order modes and polarization modes. Polarization mode addressing can be used effectively, among other things, in the construction of optical fiber polarizers, optical fiber polarization splitters, and fiber optic couplers that maintain polarization. Such device configurations are also in market demand.

  The power coupler of the present invention enables effective optical power coupling by utilizing controlled crushing of the multi-core optical fiber structure. Useful core-isolated multi-core optical fibers are utilized as the base medium, whereas the insulated core is configured as a cross-talk core between each other at -10 dB or less. This is ensured by the occurrence of a region near the core, which is characterized by a low refractive index compared to the refractive index of the coating. In an advantageous embodiment, the zone with a reduced refractive index preferably takes the form of a hole filled with air. Such a hole minimizes crosstalk, and its effect on signal propagation parameters (loss, dispersion) is advantageously small. Furthermore, the light can be incident on the coupler without theoretical loss due to the holes.

  In the basic configuration of the invention, the fiber optic coupler according to the invention is at least a single optical fiber on one side, preferably a standard single mode optical fiber, and preferably a standard single mode optical fiber. A multi-core optical fiber connected to two single optical fibers, the optical fiber can be placed in a capillary tube, and etched and / or aligned to align the cores with the core of the multi-core optical fiber. Alternatively, it may be tapered, at least one piece of the multi-core optical fiber is tapered to have a cross section of 300 μm or more and / or the hole in this cross section is collapsed. On the other hand, the power distribution is made so that the signal from a single optical fiber passes through one of the cores of a fine-structured multi-core optical fiber, preferably the central core. The hole in the optical fiber is broken and / or passes through this core to the taper region. Proper selection of hole tapering and / or crushing process parameters such that the holes in the microstructured multi-core optical fiber are broken and / or can be implemented, for example, preferably with a fusion splicer. By increasing the crosstalk between the cores, the core insulation is reduced in a controlled manner, as can be done in The length of the multicore optical fiber portion outside the tapered waist region and transition region and / or hole break region does not significantly affect the performance and effective power split of the coupler.

  In the region where the hole of the microstructured multi-core optical fiber is broken and / or tapered, the core is not insulated and a super mode is generated. Thus, by reducing the core insulation as a result of the breakage of the holes and / or by bringing the cores close together in the case of a taper, the fused cores are coupled (specific core crosstalk is increased) Therefore, the optical fiber transitions from the operation of an insulated core to the operation of a coupled core.

  As a result, the power to conduct one core is preferably divided into all cores. In an advantageous embodiment, the taper length is 300 μm or more and / or the hole in the taper portion is collapsed, and the taper length and taper ratio and / or the level of hole collapse determine the degree of power split. On the other hand, the taper length and taper ratio and / or level of crushing can be found at which the power split to all cores is advantageously even.

  Although the taper ratio is considered to be the rate of decrease of the fiber cross-sectional area of the taper waist, in an advantageous embodiment, this cross-sectional area decreases uniformly. The taper length is preferably selected by experiments aimed at the desired power split.

  Depending on the design of the microstructured multi-core optical fiber, any MxN partition can be achieved. To achieve various types of effects, the core need not be completely crushed. In addition, various divisions into specific cores can be performed by introducing external interactions due to temperature, stress (elongation, compression, twisting, bending, etc.), pressure, etc. Multi-core fiber design directly affects power splitting as a result of tapering and / or crushing.

  In another embodiment, a fiber optic coupler according to the present invention is preferably N having at least one input optical fiber, and N output optical fibers, and at least N cores with insulated cores, preferably single mode. Output optical fiber.

  Signals propagating through standard single mode optical fiber (s) are sent to a multi-core microstructured optical fiber.

  The input optical fiber (s) are connected to the multicore fiber. After passing through the multi-core optical fiber, the signal passes further through the taper and / or without crushing until the signal enters the taper region (taper transition region, then taper waist region) and / or crush region. Propagate (one or more).

  In the taper transition region, the cross-sectional area of the optical fiber: coating, core and hole diameters are reduced so that the tapering action is performed until the designed tarpa waist diameter is obtained. The reduction of the hole diameter and the approximation of the specific core and the reduction of the core diameter cause a change in the propagation characteristics, the so-called core insulation reduction, resulting in supermodes resulting in power from any core (s). There is a possibility of being transmitted to the remaining cores. In the tapered waist region, the holes are completely collapsed or their diameters remain constant.

  Depending on the desired power split, the diameter can be adjusted by selecting the diameter of the reduced hole, selecting the length of the taper (both the taper transition area and the taper waist area) and the taper waist ratio. There is sex. In this optical fiber design, there are combinations of parameters that allow for an even division of power. The fixed power division obtained at the taper is due to the “freeze” of the mode structure in the path from the transition to the part where the core is insulated. The low loss achieved with the present invention is the result of normal stimulation of the super mode performed by the characteristic tapering and / or crushing of the multi-core fiber. The crushing of the connection creates a device that functions as a splitter, but usually the loss is greater.

  The device according to the invention can also be used as follows. For example, if two wavelengths propagate through the input optical fiber, there will be different paths in each of them, and each of them will follow a given wavelength completely out of the two cores of a multi-core optical fiber, especially a dual fiber. Located in one. Thus, the tapering and / or crushing parameters can be selected so that the two wavelengths propagating in the input fiber can be successfully separated into separate cores of the multicore fiber and into the output optical fiber. The same principle of separating wavelengths into specific cores can be applied to many cores, more than two cores shown in this example, and to many more wavelengths.

  In an advantageous embodiment of the invention, for a particular application, signals are collected from only one output. This situation occurs, for example, when certain wavelengths are not simply separated but specific wavelengths must be filtered. In this case, the operation principle of the device does not change, but the purpose of the element changes. When filtering wavelengths, one or several output optical fibers can be used, the remaining fibers can be left unused, or one fiber can be connected to the output. It is advantageous from a technical point of view to connect one fiber to the output. The effective wavelength can also be filtered from the spectrum by applying a variable taper parameter to the taper adapters connected in series.

  The taper parameter can also be adapted to achieve a controlled power ratio% to input power-in this case the device operates in the function of an attenuator. In order to adjust the Q factor of the optical resonator, such an element can be used as an optical cavity for adjusting the Q factor of the optical cavity (operation as a Q switch).

  The above coupler operating principle can be usefully reversed as follows. An optical signal beam can be incident on an optical fiber connected to a multi-core fiber having an insulated core. In the non-tapered portion, the propagation does not change the characteristics related to the propagation performed in the input optical fiber. In the taper and / or squeeze region, the propagation shifts from the operation of the insulated core to the operation of the combined core. A super mode is generated, so that independently proceeding signals join at this point. At least one single core optical fiber is connected to the multicore optical fiber. Thus, the merged signal from the input core now propagates through the output optical (s) fiber with appropriate power loss. Thus, this is a “mirror” configuration of a splitter configuration that does not require structural and / or technical modifications of the system and introduces modifications of the input-output arrangement, which is referred to below as a combiner. The uses of this type of configuration are as follows. As different wavelengths propagate through each fiber including the input optical fiber, a mixed signal is obtained at the output of the output optical fiber (s). A signal having several wavelengths propagates through one optical fiber.

  In another embodiment, the coupler according to the present invention allows the construction of a device for a controlled addressing mode, which includes a multi-core optical fiber that is insulated by a zone with reduced refractive index but has a core. . Preferably, at least one core of the multi-core optical fiber is a fu mode, or a birefringent type (having a separate polarization mode), and the mode can be addressed independently (synonymous with stimulation, excitation, multiplexing) Means. This is especially true when each core of the addressing core and the addressed core is surrounded by an insulating structure that insulates one core from the other, preferably the insulating structure is preferably air or other gas, It is suitable when it has the form of a refractive index reduction zone consisting of pores filled with solid or liquid. In particular, the holes can be filled with a fiber cladding material so that the entire cladding acts as a refractive index reduction zone that insulates the core. Insulation keeps the efficiency of supermode generation (formation) on the core low-in zones that do not reduce insulation, the highest crosstalk observed between any core pair is less than -10 dB.

  An addressed core, or a multiplexed core (one of the modes is addressed / multiplexed), is a fu mode and / or birefringent core and has a distinct effective refractive index for a particular mode. Core birefringence is achieved by any well-known method, such as core ellipticity or stress conditions around the core. The terms “multimode” and “fumode” are understood to be any mode in which the core fiber has at least two modes, including separate polarization modes at the wavelengths used. Since these terms are used synonymously in the broad scope of this patent, there is no clearly defined difference between multimode fiber and fumode fiber in the literature.

  Multiplex having an effective refractive index in the vicinity of the addressed core to match the effective refractive index of at least one, preferably a single mode addressing core, or one of the modes in the addressed core. There is a core (the core in which the mode is used to excite / address a particular mode within the addressed / multiplexed core). “Specific mode stimulation / excitation” effectively forms a supermode on the core conditioned by adjusting the effective refractive index of the mode, taking into account its addressing and thus the core separately (actually observed crosstalk) ) Means that it is possible. After reducing the insulation, the cores are combined, where supermodes that are generated in both cores, not already in individual modes, become a problem.

  There are two roles in selecting the effective refractive index of a mode so that each core has a distinct refractive index and the other core has a tuned effective refractive index. First, it reduces crosstalk between addressing cores (inefficient formation of supermodes by separating the effective refractive index of each mode pair), and secondly, cores addressed and cores addressed by phase matching Allows selective crosstalk between the two (efficient formation of super mode). Various shaping capabilities of the super mode in the area with reduced (reduced) insulation are made possible by selecting the refractive index of the mode in the structure with the insulated core-the refractive index is close in certain modes As such, they form an efficient supermode and are therefore addressed in the form of addressed modes (fundamental mode, higher order mode, polarization mode) for the power present in the core addressing in the form of addressing mode The power present in the core is increased.

  At least a dual-core fiber multi-core fiber having an insulated core is connected to at least one, at least a single-core input fiber, and at least one, at least a single-core output fiber is attached to the opposite side of the multi-core fiber, The input and output fibers attached to the fiber can be placed in a capillary tube and can be etched and / or tapered so that their cores are preferably aligned with the core of the multi-core fiber (fan-in-fan). Out element type). Within at least one segment of the multi-core fiber, the core insulation is reduced (reduced) by reducing (reducing) the size of the zone of reduced refractive index in the vicinity of the core and / or by crushing their structure. Is done. In regions where core insulation could be reduced, supermodes are formed in the particular addressing core (s) and / or addressed core (s). The ratio between the power present in the core addressed in the form of the mode addressed at the output of the multicore fiber and the power present in the core addressed in the form of the addressing mode at the input of the multicore fiber is greater than -5 dB , Preferably greater than −3 dB. If only one addressing core is excited, the form of the unaddressed mode (depending on the initially excited addressing mode) within the specific addressing core (s) and addressed core (s) The ratio of the power present at the output of the multicore to the power at the input of the multicore in the form of an addressing mode within the initially excited addressing core is less than -10 dB, preferably less than -14 dB. Highly efficient supermode formation (defined as final crosstalk) is achieved by adjusting the effective refractive index of each mode pair before insulation reduction (after insulation reduction already described for the supermode).

  The structure of the multi-core fiber is preferably tapered and / or the holes in the structure are preferably at least in one place and at least the appearance of power in the form of an addressed mode within the addressed core can be observed It is crushed by the part. Preferably, the minimum length of taper and / or hole breakage is 300 μm. The length of taper and / or hole breakage is preferably a maximum length equal to the used portion of the multi-core fiber. The taper ratio is preferably 0 to 95%. The taper ratio is considered as a reduction in the cross-sectional area of the tapered waist region, but in an advantageous embodiment, this cross-sectional area is uniformly reduced. Preferably, the optical fiber is coated.

  In a preferred embodiment, a single mode input single core optical fiber at the wavelength used, preferably seven of which are connected to a particular core of a multi-core fiber, preferably a 7-core fiber. The refractive index profile and diameter of the core addressing the multicore fiber are selected such that all addressing modes of the multicore fiber have different effective refractive indices. The addressed core is a fu mode, and the refractive index of that mode is chosen to suit the effective refractive index of each of the modes within the addressing core. In regions where insulation is not reduced, the supermode is formed such that the highest crosstalk observed between any core pair is less than -10 dB.

  In certain parts, preferably 300 μm, the refractive index is reduced and the zone separating the cores is crushed or the dimensions are reduced (eg by tapering), so that the core insulation is reduced. A super mode is formed and crosstalk increases. The ratio between the power present in the core addressed in the form of the mode addressed at the output of the multicore fiber and the power present in the core addressed in the form of the addressing mode at the input of the multicore fiber is greater than -5 dB , Preferably greater than −3 dB. If only one addressing core is excited, the form of the unaddressed mode (depending on the initially excited addressing mode) within the specific addressing core (s) and addressed core (s) The ratio of the power present at the output of the multicore to the power at the input of the multicore in the form of an addressing mode within the initially excited addressing core is less than -10 dB, preferably less than -14 dB. The power level distribution of each addressed mode appearing at the end of the modified portion is “frozen” and this state is further transported by the unmodified portion of the multicore fiber.

  In particular, the single-core fumode fiber is preferably connected to the output end of the multi-core fiber with the same or similar characteristics as the addressed core of the multi-core fiber. Therefore, in the fumode fiber, transmission is realized by mode multiplexing. Therefore, the above-described multi-core fiber whose core insulation is reduced by being controlled is an element (coupler) that enables an addressing mode in the fu mode fiber. With this configuration, particularly a 7-core fiber, the six fundamental modes of the addressing core address the six higher order modes of the addressed core. The fundamental mode of the addressed core is excited by first connecting the fiber to this core.

  Similarly, the signal in the fu mode fiber can be demultiplexed using the coupler according to the present invention-the information transmitted in the fu mode fiber and encoded in the individual modes is individually And can be separated into separate optical fibers.

  In another preferred embodiment, a single mode input single core optical fiber at the wavelength used, preferably three of which are connected to a particular core of a multi-core fiber, preferably a 4-core fiber .

  The refractive index profile and diameter of the core addressing the multicore fiber are selected such that all addressing modes of the multicore fiber have different effective refractive indices. The addressed core is a fu mode, and the refractive index of that mode is chosen to suit the effective refractive index of each of the modes within the addressing core. In regions where insulation is not reduced, the supermode is formed such that the highest crosstalk observed between any core pair is less than -10 dB.

  In certain parts, preferably 300 μm, the refractive index is reduced and the zone separating the cores is crushed or the dimensions are reduced (eg by tapering), so that the core insulation is reduced. A super mode is formed and crosstalk increases. The ratio between the power present in the core addressed in the form of the mode addressed to the output of the multicore fiber and the power present in the core addressed in the form of the addressing mode to the input of the multicore fiber is greater than -5 dB , Preferably greater than −3 dB. If only one addressing core is excited, the form of the unaddressed mode (depending on the initially excited addressing mode) within the specific addressing core (s) and addressed core (s) The ratio of the power present at the output of the multicore to the power at the input of the multicore in the form of an addressing mode within the initially excited addressing core is less than -10 dB, preferably less than -14 dB. The power level distribution of each addressed mode appearing at the end of the modified portion is “frozen” and this state is further transported by the unmodified portion of the multicore fiber.

  In particular, a single-core fumode fiber is preferably connected to the output end of a multi-core fiber having the same or similar characteristics as the addressed core of the multi-core fiber. Therefore, in the fumode fiber, transmission is realized by mode multiplexing. Therefore, the above-described multi-core fiber whose core insulation is reduced by being controlled is an element (coupler) that enables an addressing mode in the fu mode fiber. With this configuration, one basic mode and two higher-order modes in the core to which the three basic modes of the addressing core are addressed are addressed.

  Similarly, the signal in the fu mode fiber can be demultiplexed using the coupler according to the present invention-the information transmitted in the fu mode fiber and encoded in the individual modes is individually And can be separated into separate optical fibers.

  In another preferred embodiment, the single core optical fiber is connected to a multicore optical fiber, preferably a dual core addressing core, that propagates through the core to which the signal is addressed. The addressed core of a multicore fiber has a high birefringence—this polarization mode has a separate effective refractive index. The addressing core of a multi-core fiber has a low birefringence—this polarization mode has an equal mode effective refractive index and can therefore be referred to generically as a single mode core. One of the polarization modes in the addressed core (polarization mode x) has an effective refractive index equal to the effective refractive index of the mode in the addressing core of the multicore fiber.

  In some parts, preferably at least 300 μm, the refractive index is reduced and the zone separating the cores is collapsed or its diameter is reduced (eg by tapering), so that the insulation of the core is reduced. A super mode is formed and crosstalk increases. The ratio between the power present in the core addressed in the form of the mode addressed to the output of the multicore fiber and the power present in the core addressed in the form of the addressing mode to the input of the multicore fiber is greater than -5 dB , Preferably greater than −3 dB. If only one addressing core is excited, the form of the unaddressed mode (depending on the initially excited addressing mode) within the specific addressing core (s) and addressed core (s) The ratio of the power present at the output of the multicore to the power at the input of the multicore in the form of an addressing mode within the initially excited addressing core is less than -10 dB, preferably less than -14 dB. The power level distribution of each addressed mode appearing at the end of the modified portion is “frozen” and this state is further transported by the unmodified portion of the multicore fiber.

  One polarization mode propagates through an addressed core with high birefringence. After the portion where the hole is broken, the signal propagates through a highly birefringent core where only one propagation mode is effectively excited. A birefringent polarization maintaining fiber is preferably connected to the core having high birefringence. Since this method of addressing the polarization mode allows efficient addressing of one polarization mode, a coupler having the function of an optical fiber polarizer is constructed.

  In another preferred embodiment, the single core optical fiber is connected to the addressing core of a preferably 3-core multi-core optical fiber. The addressing core of a multi-core fiber has a low birefringence—this polarization mode has an equal mode effective refractive index and can therefore be referred to generically as a single mode core. High birefringence in the addressed core in the vicinity of the addressing core-this polarization mode has a distinct effective refractive index. One of the polarization modes in the first addressed core (polarization mode x) has an effective refractive index equal to the effective mode refractive index in the addressing core of the multi-core fiber, and in the second addressed core. One of the polarization modes (polarization mode y) has an effective refractive index equal to the effective refractive index of the mode in the addressing core of the multi-core fiber.

  In some parts, preferably at least 300 μm, the refractive index is reduced and the zone separating the cores is collapsed or the diameter is reduced (eg by tapering), so that the insulation of the core is reduced, A super mode is formed and crosstalk is increased. The ratio between the power present in the core addressed in the form of the mode addressed to the output of the multicore fiber and the power present in the core addressed in the form of the addressing mode to the input of the multicore fiber is greater than -5 dB , Preferably greater than −3 dB. If only one addressing core is excited, the form of the unaddressed mode (depending on the initially excited addressing mode) within the specific addressing core (s) and addressed core (s) The ratio of the power present at the output of the multicore to the power at the input of the multicore in the form of an addressing mode within the initially excited addressing core is less than -10 dB, preferably less than -14 dB. The power level distribution of each addressed mode appearing at the end of the modified portion is “frozen” and this state is further transported by the unmodified portion of the multicore fiber.

  After the part where the hole is broken, the signal propagates through a highly birefringent core where one polarization mode—the polarization mode (x) within one of the addressing cores and the second addressing core. Only the polarization mode (y) within is effectively excited. The polarization maintaining fiber is preferably connected to a birefringent core having high birefringence. This method of addressing the polarization mode allows efficient addressing of one polarization mode, thus constructing a coupler with the function of an optical fiber polarization splitter.

  In another preferred embodiment, the birefringent single core optical fiber is connected to a multicore optical fiber, preferably a dual core addressing core. The addressing core of a multicore fiber has a high birefringence—this polarization mode has a distinct effective refractive index. The addressed core of the multicore fiber in the vicinity of the addressing core also has a high birefringence—this polarization mode has a distinct effective refractive index. Preferably, the core to be addressed and the core to be addressed are of the same type.

  The addressed core has polarization modes (x) and (y), and these modes have an effective refractive index that matches the refractive index of the polarization modes (x) and (y) in the addressing core.

  In some parts, preferably at least 300 μm, the refractive index is reduced and the zone separating the cores is collapsed or the diameter is reduced (eg by tapering), so that the insulation of the core is reduced, A super mode is formed and crosstalk is increased. The ratio between the power present in the core addressed in the form of the mode addressed to the output of the multicore fiber and the power present in the core addressed in the form of the addressing mode to the input of the multicore fiber is preferably -5 dB Greater than and preferably less than -3 dB. The power level distribution of each addressed mode appearing at the end of the modified portion is “frozen” and this state is further transported by the unmodified portion of the multicore fiber.

  After the part where the hole is broken, the signal propagates through a highly birefringent core where the polarization mode-polarization modes (x) and (y) are excited. The polarization maintaining fiber is preferably connected to a birefringent core having high birefringence. This method of addressing the polarization mode allows for efficient addressing of one polarization mode, thus constructing a coupler (splitter) that maintains the polarization.

  In another preferred embodiment that enables the implementation of add-drop multiplexing consisting of adding / removing one of the channels to / from a signal propagating through one core, in a preferred embodiment, a multi-core optical fiber, preferably a core A dual core fiber is used that is insulated by a refractive index reduction zone. The multi-core fiber suitably has at least one single mode core and preferably at least one fu mode core. The effective refractive index of the mode in the single mode core is matched with the effective refractive index of one mode in the fu mode core. Two single-core optical fibers are attached to both sides of the multi-core fiber, preferably a dual-core fiber, preferably with the core aligned with the core of the dual-core fiber. In areas where insulation is not reduced, a super mode is formed (inefficient formation) such that the maximum crosstalk observed between any core pair is less than -10 dB.

  In certain parts, preferably 300 μm, the refractive index is reduced and the zone separating the cores is crushed or the diameter is reduced (eg by tapering), so that the core insulation is reduced. A super mode is formed and crosstalk increases. The ratio between the power present in the core addressed in the form of the mode addressed to the output of the multicore fiber and the power present in the core addressed in the form of the addressing mode to the input of the multicore fiber is greater than -5 dB , Preferably greater than −3 dB. If only one addressing core is excited, the power present at the output of the multi-core in the form of the unaddressed mode (depending on the initial excited addressing mode) within the specific addressing core (s) and the initial The ratio to the power at the input of the multi-core in the form of an addressing mode in the excited addressing core is less than -10 dB, preferably less than -14 dB. The power level distribution of each addressed mode appearing at the end of the modified portion is “frozen” and this state is further transported by the unmodified portion of the multicore fiber.

  The mode in the single mode core and one of the modes in the fu mode core have a matched refractive index before reducing the insulation, so a super mode is formed in the area where the insulation is reduced. Therefore, the mode from the single mode core addresses the mode in the fuse mode core, and the mode from the mode in the fuse mode core addresses the mode in the single mode core. Therefore, a type of multiplexer / demultiplexer called an add-drop multiplexer / demultiplexer can be realized. Then, both the single mode core and the fu mode core are both the addressing core and the addressed core.

  In an advantageous embodiment of the invention, the optical fiber can be used to change the taper length and taper tension by deforming the optical fiber or changing its temperature, in particular the optical fiber. It is wound or attached to a piezoelectric or mechanical device that switches signals between specific cores during operation with the same optical switch function.

While the subject matter of the present invention has been presented in detail in the examples and drawings, they do not exclude the possibility of construction of the present invention according to the operating principles described herein.
An advantageous embodiment of the invention, namely a standard single-mode optical fiber (1) with a cross-section (1A-1A) and a microstructured multi-core optical fiber (2) with a tapered region are joined and then It is a figure in which the optical fiber (2) is connected to a bundle of output optical fibers arranged in a narrow tube (3) whose cross section (3A-3B) is shown, and the aspect ratio is not maintained. Section AA is a section of a microstructured optical fiber that is not tapered, and section BB is a tapered transition region of a microstructured multicore optical fiber having a collapsed / broken hole. FIG. 5 is an enlarged view of a tapered portion of a multi-structure optical fiber having a fine structure in which the aspect ratio is not maintained, showing a waist region of the fine structure multi-core optical fiber having a hole whose cross-section C-C is completely crushed. Part (a) is an untapered fiber area with a total diameter (d1), part (b) is a tapered transition region where the taper diameter is reduced / expanded, and part (c) is characterized by a diameter (d2). It is a figure which shows the taper part of the taper of a multi-core optical fiber which is a waist part of the taper. 1 is a cross-sectional view of a standard single mode optical fiber (1) having a core (4) of diameter (d3) and a cladding (5) of diameter (d4). To construct the present invention having a core (4) of diameter (d5), a cladding (5) of diameter (d6), and a hole (6) of diameter (d7), which is not tapered. It is a figure which shows the model of the multi-core optical fiber of the fine structure which can be used. A microstructured multi-core optical fiber having a partially collapsed hole (6) of diameter (d8), a reduced diameter core (4) of diameter (d9), and a reduced diameter cladding (5) of diameter (d10) FIG. FIG. 2 is a view showing a microstructured multi-core optical fiber with a completely collapsed hole, characterized by a reduced diameter core (4) having a diameter (d11) and a reduced diameter cladding (5) having a diameter (d12). A core (4) of a single mode optical fiber having a diameter (d13), a cladding (5) of a single mode optical fiber of diameter (d14), an inner diameter (d14) of a capillary (capillary), and an outer diameter (d15) of the capillary FIG. 2 shows a bundle of standard single-mode optical fibers arranged in a capillary tube (7). FIG. 5 shows an advantageous embodiment of the invention operating as N × N optical fiber couplers. Advantageous of the present invention having two inputs (outputs) and seven inputs (outputs), in which the glass rod (8) serving as a geometrical filling of the narrow tubes (7) is displayed in the cross section 4A-4A It is a figure which shows embodiment. To construct the present invention having a core (4) of diameter (d5), a cladding (5) of diameter (d6), and a hole (6) of diameter (d7), which is not tapered. It is a figure which shows the model of the dual core optical fiber of the fine structure which can be used. FIG. 2 shows an advantageous embodiment of the invention with two inputs (outputs) and one output (inputs), wherein (1) is a single mode optical fiber and (2) is a multi-core optical fiber. An advantageous embodiment of Example 6 of the present invention, namely a bundle of standard single mode optical fibers (1) arranged in a capillary (3) with a cross section (3A-3A) shown, and a taper is shown. A microstructured multi-core fiber (2) is bonded, then the fiber (2) is bonded to a fumode fiber (9) with a cross section (9A-9A), the aspect ratio is not retained FIG. It is sectional drawing of the fu mode optical fiber (9) of Example 6 which has the core (4) of diameter (d17), and the clad (5) of diameter (d16). A single mode core (4.1-4.6) of diameter (d5.1-d5.6), a fumode core (10) of diameter (d17) and lattice constant (Λ), and a cladding of diameter (d6) FIG. 6 shows an exemplary multi-core fiber of Example 6 that can be used to construct the present invention, having (5), and holes (6) of diameter (d7) that are not tapered and collapsed. FIG. Section AA is a section of a fine-structured optical fiber that is not tapered, and section BB is a tapered transition region of a microstructured multi-core optical fiber having a partially collapsed hole. FIG. 9 is an enlarged view of a taper portion of a microstructured multi-core optical fiber of Example 6 in which the waist region of the microstructured multi-core optical fiber having a hole collapsed is shown, which also does not maintain the aspect ratio. It is a figure which shows the transmission system based on the spatial multiplexing which consists of the coupler of Example 6 by this invention for constructing | requiring a multiplexer and a demultiplexer correspondingly in the start end of a fu mode fiber (9), and a termination | terminus. An advantageous embodiment of Example 7 of the present invention, namely a bundle of standard single mode optical fibers (1) placed in a capillary tube (3) and a finely structured 4-core light (2 ), And then the fiber (2) is joined to the fumode fiber (9) shown in cross section (9A-9A), without maintaining the aspect ratio. A single mode core (4.1-4.3) of diameter (d5.1-d5.3), a fumode core (10) of diameter (d17) and lattice constant (Λ), and a cladding of diameter (d6) Example multi-core fiber of Example 7 that can be used to construct the present invention, (5), and pores (6) of diameter (d7), which are not tapered and not crushed FIG. Example 8 of an advantageous embodiment of the present invention, ie a single mode optical fiber (1) and a microstructured multi-core fiber shown with a taper are joined, and then the fiber (2) maintains polarization. FIG. 3 is a diagram in which the aspect ratio is not maintained, which is bonded to a birefringent fiber (11). Single mode core (4) with diameter (d5), birefringent core (12) with short axis (d18) and long axis (d19) with lattice constant (Λ), clad (5) with diameter (d6), and diameter FIG. 9 shows an exemplary dual core fiber of Example 8 that can be used to construct the present invention with (d7) holes (6) and not tapered and crushed; Example 9 of an advantageous embodiment of the invention, namely a single-core optical fiber (1) and a microstructured multi-core fiber (2) shown with a taper are joined, and then the fiber (2) maintains polarization. It is a figure joined to the birefringent fiber (11) to which the aspect ratio is not hold | maintained. Single mode core (4) with diameter (d5), birefringent core (12.1 and d19.2) with short axis (d18.1 and d18.2) and long axis (d19.1 and d19.2) with lattice constant (Λ) 12.2), clad (5) with diameter (d6), and holes (6) with diameter (d7), used to construct the present invention, which is not tapered and crushed FIG. 10 illustrates an exemplary dual core fiber of possible Example 9. Example 10 of an advantageous embodiment of the invention, namely a single-core optical fiber (13) and a microstructured multi-core fiber (2) shown in taper are joined, and then the fiber (2) maintains polarization. It is a figure joined to the birefringent fiber (11) to which the aspect ratio is not hold | maintained. Single mode core (4) with diameter (d5), birefringent core (12.1 and d19.2) with short axis (d18.1 and d18.2) and long axis (d19.1 and d19.2) with lattice constant (Λ) 12.2), clad (5) with diameter (d6), and holes (6) with diameter (d7), used to construct the present invention, which is not tapered and crushed FIG. 11 illustrates an exemplary dual core fiber of possible Example 10. Example 11 of an advantageous embodiment of the invention, namely single-core fibers (1) and (9), and a microstructured multi-core fiber (2) shown with a taper are joined, then fiber (2) Are joined to the output single core fibers (1) and (9), and the aspect ratio is not maintained. A single mode core (4) of diameter (d5), a fumode core (10) of diameter (d17) and lattice constant (Λ), a cladding (5) of diameter (d6), and a hole of diameter (d7) (6 ) And an exemplary dual core fiber of Example 11 that can be used to construct the present invention without tapering and crushing.

  The coupler according to the invention comprises an input optical fiber (1), which is then an optical fiber in the form of a microstructured 7-core optical fiber (2) connected to a bundle of 7-core output optical fibers (3). Connected to (2).

  The signal propagates through Corning's standard single mode optical fiber (1), SMF-28e, and is then routed to the central core of the microstructured multi-core optical fiber (2).

  A single-core optical fiber (1) is preferably connected to the multi-core optical fiber (2), preferably by fusion splicing, using a fusion splicer (Vytren GPX-3400 or Fujikura FSM 70) (Splicing).

  After being sent to the multi-core optical fiber (1), the signal propagates through the central core in part (a) until it reaches the tapered part (b, c). In the tapered part (b) which is preferably 5 mm or more, the diameter of the cross section of the optical fiber: the clad (5), the core (4) and the hole (6) is reduced (reduced).

  The reduction of the cross-section (6) changes the propagation characteristics, so-called core insulation reduction, so that a super mode is generated and power is transmitted from any core (s) to the remaining cores. Propagation therefore shifts from isolated core operation to coupled core operation. The equal division of power into all cores is mainly performed in the part where the hole is completely collapsed (b) and the part where the diameter of the hole is reduced / increased (c). The length of the part (c) is 5 mm. After part (c) comes the taper transition zone (b). The power in each core continues to propagate independently due to the appearance (encounter) of the holes (6). In part (a), after passing through the taper, there are seven cores (4), and a proportional amount of power propagates through these cores. With the advent of the holes (6), the signal from one core does not affect the signal propagation from the other core and can therefore still be treated as the propagation of an isolated core. The multi-core optical fiber whose seven cores carry signals is connected to a single bundle of single mode optical fibers (3). The connection is made by a fusion splicing process, and the manufacture of such devices and their connection with multicore optical fibers are described in detail in the appropriate literature. After passing through a bundle of single-mode optical fibers (3), seven signals of independent single-mode optical fibers are obtained, these signals emanating from one single-mode optical fiber (1) and to a specific recipient Can be redirected.

  The values of the taper portions (b, c) are b = 5 mm and c = 5 mm, and the taper ratio of the multicore fiber is the following parameters of the multicore fiber: core diameter d5 = 6.5 μm, clad diameter d6 = 125 μm, hole diameter d7 = 5.8 μm, lattice constant (Λ) = 8.2 μm, and 20% (the waist diameter of the portion (c) is 100 μm at the maximum).

  In an advantageous embodiment, the coupler according to the invention is used to divide the power into a bundle of two optical fibers (1) to seven optical fibers (3), the example being a microstructured multi-core optical fiber (2 ). Single mode optical fiber (1) is Corning SMF-28e + fiber.

  Two single-core optical fibers (1) are connected to the multi-core optical fiber (2), preferably by fusion splicing, using a fusion splicing device (Vytren GPX-3400 or Fujikura FSM 70). On the other hand, each single mode optical fiber in the bundle is connected to a different core of the multi-core optical fiber. After being sent to the multi-core optical fiber (2), the signal further propagates through the part (a) in the two cores until it reaches the tapered part (b, c). Preferably, the diameter of the cross section of the optical fiber: the clad (5), the core (4), and the hole (6) is reduced by a tapered portion (b) of 5 mm or more.

  Due to the reduced diameter of the cross section (6), the propagation characteristics, so-called core insulation reduction, change, and as a result, the super mode is generated so that power is transferred from any core (s) to the remaining cores. Is done. Propagation therefore shifts from isolated core operation to coupled core operation. The equal division of power into all cores is mainly performed in the part where the hole is completely collapsed (c) and the part where the diameter of the hole is reduced / increased (b).

  The length of the part (c) is 7 mm. After part (c) comes the taper transition zone (b). The power in each core continues to propagate independently due to the appearance of the holes (6). In part (a), after passing through the taper, there are seven cores (4), and a proportional amount of power propagates through these cores. With the advent of the holes (6), the signal from one core does not affect the signal propagation from the other core and can therefore still be treated as the propagation of an isolated core. The multi-core optical fiber whose seven cores carry signals is connected to a single bundle of single mode optical fibers (3). The connection is made by a fusion splicing process, and the manufacture of such devices and their connection with multicore optical fibers are described in detail in the appropriate literature. After passing through a bundle of single-mode optical fibers (3), seven signals of independent single-mode optical fibers are obtained, these signals emanating from the two single-mode optical fibers (1) and to a specific recipient Can be redirected.

  The values of the taper portions (b, c) are b = 5 mm and c = 5 mm, and the taper ratio of the multicore fiber is the following parameters of the multicore fiber: core diameter d5 = 6.5 μm, clad diameter d6 = 125 μm, hole diameter d7 = 5.8 μm, lattice constant (Λ) = 8.2 μm, and 20% (the waist diameter of the portion (c) is 100 μm at the maximum).

  In the advantageous embodiment of the invention shown in FIG. 9, the invention is used to couple from each of the seven input optical fibers (1) to a bundle of seven output optical fibers (3), A multi-core optical fiber (2) is used. The signal propagates through a standard single-mode optical fiber (1), Corning's SMF-28e + fiber, and then sent to a microstructured multi-core optical fiber (2).

  A single mode optical fiber (1) is connected to the multi-core optical fiber (2), preferably by fusion splicing, using a fusion splicing device (Vytren GPX-3400 or Fujikura FSM 70). After being sent to the multi-core optical fiber (2), the signal propagates through the portion (a) that is still within the seven cores of the multi-core fiber until it reaches the taper (b, c). Preferably, the diameter of the cross section of the optical fiber: the clad (5), the core (4), and the hole (6) is reduced by a tapered portion (b) of 5 mm or more. Due to the reduced diameter of the cross-section (6), the propagation characteristics, so-called core insulation reduction, change, and as a result, the super mode is generated, so that the signal can be transmitted between the cores. Propagation therefore shifts from isolated core operation to coupled core operation. The mixing of the signals between the cores takes place mainly in the part where the hole is completely collapsed (c) and in the part where the diameter of the hole is reduced / increased (b). The length of the part (c) is 7 mm. After part (c) comes the taper transition zone (b). The power in each core continues to propagate independently due to the appearance of the holes (6). In part (a), after passing through the taper, there are seven cores (4), and a proportional amount of power propagates through these cores. With the advent of the holes (6), the signal from one core does not affect the signal propagation from the other core and can therefore still be treated as the propagation of an isolated core. The multi-core optical fiber whose seven cores carry signals is connected to a single bundle of single mode optical fibers (3). The connection is made by a fusion splicing process, and the manufacture of such devices and their connection with multicore optical fibers are described in detail in the appropriate literature. After passing through a bundle of single-mode optical fibers (3), seven signals of independent single-mode optical fibers are obtained, these signals contain information from all seven input optical fibers, and a specific recipient. Can be redirected to.

  The values of the taper portions (b, c) are b = 5 mm and c = 7 mm, and the taper ratio of the multicore fiber is the following parameters of the multicore fiber: core diameter d5 = 6.5 μm, clad diameter d6 = 125 μm, hole diameter d7 = 5.8 μm, lattice constant (Λ) = 8.2 μm, and 20% (the waist diameter of the portion (c) is 100 μm at the maximum).

  In another embodiment of the invention shown in FIG. 12, where the invention is used to switch between two input wavelengths between specific output optical fibers, a microstructured multi-core optical fiber (2) is utilized. In this embodiment, this may be the dual core optical fiber shown in FIG. The signal propagating through Corning's standard single-mode optical fiber (1), SMF-28e, is then sent to one of the cores of a microstructured multi-core optical fiber (2).

  A single mode optical fiber (1) is connected by fusion splicing to a multi-core optical fiber (2) using a fusion splicing device (Vytren GPX-3400 or Fujikura FSM 70). After being sent to the multi-core optical fiber (2), the signal further propagates in the core in the portion (a) to which the multi-core fiber is connected until reaching the tapered portions (b, c). Preferably, the diameter of the cross section of the optical fiber: the clad (5), the core (4), and the hole (6) is reduced by a tapered portion (b) of 6 mm or more. Due to the reduced diameter of the cross section (6), the propagation characteristics, so-called core insulation reduction, change, and as a result, a super mode is generated so that power can be transmitted from the initial core carrying the signal to the second core. become. Propagation therefore shifts from isolated core operation to coupled core operation. Depending on the length of the taper, the signal can be separated between the cores at any ratio. When the taper portion (taper waist region) is 10 mm, the signal propagates only through the core to which the single core fiber is connected. In the case of a taper portion (taper waist region) extended by 8 mε, the signal is completely sent to a nearby core. The intermediate value corresponds to the situation where power propagates through both cores in various relations. The taper length can be changed by the piezoelectric around which the multi-core optical fiber (2) is wound or attached, and the switching of signals between specific cores occurs while the device operates with the same optical switch function.

  The values of the taper portions (b, c) are b = 5 mm and c = 10 mm, and the taper ratio of the multicore fiber is the following parameters of the multicore fiber: core diameter d5 = 125 μm, clad diameter d6 = 6.6 μm, hole diameter d7 = 6.6 μm, lattice constant (Λ) = 7.6 μm, 30%.

  In the advantageous embodiment of the invention shown in FIG. 12, where the invention is used to separate two input wavelengths into a specific output optical fiber, a microstructured multi-core optical fiber (2) is utilized. In this embodiment, this may be the dual core optical fiber shown in FIG. A signal propagating through Corning's standard single mode optical fiber (1), SMF-28e, is sent to one of the cores of a microstructured multi-core optical fiber (2). In this embodiment, two wavelengths, 1550 nm and 1310 nm, propagate through the input optical fiber. A single mode optical fiber (1) is connected by fusion splicing to a multi-core optical fiber (2) using a fusion splicing device (Vytren GPX-3400 or Fujikura FSM 70). After being sent to the multi-core optical fiber (2), the signal further propagates in the core in the portion (a) to which the multi-core fiber is connected until reaching the tapered portions (b, c). Preferably, the diameter of the cross section of the optical fiber: the clad (5), the core (4), and the hole (6) is reduced by a tapered portion (b) of 3 mm or more. By reducing the diameter of the cross section (6), the propagation characteristics, so-called core insulation reduction, change, and as a result, a super mode is generated, so that signals can be transmitted from the first signal carrying core to the second core. become. Propagation therefore shifts from isolated core operation to coupled core operation. Depending on the taper length, the signal can be separated between the cores at any ratio. When the taper portion (taper waist region) is 6 mm, the wavelength of 1550 nm propagates only through the core to which the single core fiber is connected. Further, the wavelength of 1310 nm propagates only in the nearby core. When the taper portion (taper waist region) is extended by 8 mε, in this embodiment, other wavelengths of 1550 nm and 980 nm are efficiently separated between the cores. Since the fiber can be stretched, the taper length can be changed, and thus various wavelength separation configurations are possible. Also, the wavelengths described herein have a taper length that allows the two wavelengths to be separated into specific communication channels. Such a field of application of the present invention is the implementation of the concept of WDM (wavelength division multiplexing) couplers.

  The values of the taper portions (b, c) are b = 3 mm and c = 6 mm, and the taper ratio of the multi-core fiber is the following parameters of the multi-core fiber: core diameter d5 = 6.6 μm, clad diameter d6 = 125 μm, hole diameter d7 = 6.6 μm, lattice constant (Λ) = 7.6 μm, 30%.

  With the coupler according to the invention, a core insulated in a reduced area of refractive index 6 in the form of air-filled holes and a single mode core (4.1, 4.2, 4.3, 4.4 with a wavelength of 1550 nm). , 4.5, 4.6) can be constructed for controlled mode addressing comprising a multi-core (7-core) optical fiber (2), which has a graded refractive index. And a fundamental mode having a different distribution and effective refractive index. For the 7-core fiber (2) with an insulating core, using a fan-in / fan-out type element, a 7-input single-core fiber (2) is placed in the capillary tube (3), opposite the multi-core fiber. A single-core fumode output fiber (9) is attached to the side, and in the multi-core optical fiber (2) portion, the insulation is reduced by crushing the structure of the insulating hole 6. Geometric midpoints of the microstructure elements (holes and cores) are arranged on the hexagonal lattice, the lattice constant (Λ) is 20 μm, the diameter of the insulating holes is 10 μm, and the core (10) -addressing The core multicore that is made has a graded refractive index profile, which is a fu mode and has a distinct effective refractive index for a particular mode. In the vicinity of the addressed core (10) is an addressing core (4.1 to 4.6) having a graded refractive index distribution, and the effective refractive index of the mode is determined for each of the addressed cores (10). Is selected to match the effective refractive index of the mode.

  In the area where the insulation is not reduced, a super mode is formed (inefficient formation) so that the maximum crosstalk observed between any pair of cores is less than -10 dB. The structure of the multi-core fiber (2) is modified so that in some parts the structure of the hole (6) is crushed, this part being able to efficiently form a supermode on the addressing core and the addressed core. There is enough length. The length of the collapsed portion of the hole (6) is 5 mm, and the taper ratio is 0.5%.

  (C) = 5 mm, reduced core insulation is formed as a result of collapse of the holes separating the cores, super mode is formed and crosstalk is increased-addressing at the output of multi-core fiber The ratio between the power present in the addressed core in the form of the addressed mode and the power present in the addressing core in the form of the addressing mode at the input of the multicore fiber is greater than -3 dB. If only one addressing core is excited, the mode of the unaddressed mode (depending on the initially excited addressing mode) within the specific addressing core (s) and addressed core (s) The ratio between the power present at the output of the multicore and the power in the form of the addressing mode of the core that is initially excited at the multicore input is less than -14 dB. The power level distribution of each addressed mode appearing at the end of the modified portion is “frozen” and this state is further transported by the unmodified portion of the multicore fiber.

  The single-core fumode fiber (9) is connected to the output end of the multi-core fiber (2) having the same or similar characteristics as the addressed core (10) of the multi-core fiber (2). Therefore, in the single-core fumode fiber (9), mode multiplexing is performed using seven modes. Therefore, the above-described coupler configuration in the multi-core fiber in which the insulation of the core is controlled (reduced) is an element (coupler) that enables an addressing mode in the fu mode fiber.

  Similarly, the signal in the fu mode fiber can be demultiplexed using the coupler according to the present invention-the information transmitted in the fu mode fiber and encoded in a particular mode is individually And can be separated into separate optical fibers. A transmission system using mode multiplexing can be constructed by using couplers in a multiplexer and demultiplexer configuration with connections to a fumode optical fiber (FIG. 17).

The dimensions of diffuser-mode fiber (9): clad diameter d16 = 125 [mu] m; diffuser-mode core (10) - the diameter d17 = 20μm, SiO ₂ doped with 5.8 mole% of GeO ₂
Dimensions of multicore fiber (2):
- Few-mode core (10) - the diameter d17 = 20 [mu] m, _SiO doped with 5.8 mole% of GeO ₂ 2;
- Core (4.1) - diameter d5.1 = 12.6μm, _SiO doped with 5.8 mole% of GeO ₂ 2;
- Core (4.2) - diameter d5.2 = 8μm, _SiO 2 doped with 5.8 mole% of GeO _2;
- Core (4.3) - diameter d5.3 = 6.4μm, _SiO doped with 5.8 mole% of GeO ₂ 2;
- Core (4.4) - diameter d5.4 = 5.4μm, _SiO doped with 5.8 mole% of GeO ₂ 2;
- Core (4.5) - diameter d5.5 = 4.4μm, _SiO doped with 5.8 mole% of GeO ₂ 2;
- Core (4.6) - diameter d5.6 = 2μm, _SiO 2 doped with 5.8 mole% of GeO _2;
- cladding (5) - diameter d6 = 250 [mu] m, _SiO doped with 0 mol% of GeO ₂ 2;
-Lattice constant (Λ) = 20 μm
Size of hole (6): Diameter d7 = 10 μm
Taper parameters:
-Part (b) = 0 mm
-Part (c) = 5 mm
-Diameter d1 = d2 = 250 μm
-Taper ratio = 0.5% (no taper due to hole breakage)

  The invention of Embodiment 6 is shown in FIG. 3, FIG. 13, FIG. 14, FIG. 15, FIG. In this configuration, the six fundamental modes of the addressing core address the six higher order modes of the core to be addressed. The fundamental mode of the addressed core is excited by first connecting the fiber to this core.

  With the coupler according to the invention, a core insulated in the area of reduced refractive index (6) in the form of air-filled holes and a single mode core (4.1, 4.2, 4.3) with a wavelength of 1550 nm, It is possible to construct an element for a controlled addressing mode having a multi-core optical fiber (2) with a core having a graded refractive index profile and a fundamental mode with a different effective refractive index. The multi-core 4-core fiber (2) using the fan-in / fan-out type element has a 3-input single-core fiber (2) arranged in the narrow tube (3), and the single-core is opposite to the multi-core fiber. In the multi-core optical fiber (2), the insulation is reduced by crushing the structure of the insulating hole (6). Geometric midpoints of the microstructure elements (holes and cores) are arranged on the hexagonal lattice, the lattice constant (Λ) is 20 μm, the diameter of the insulating holes is 10 μm, and the core (10) -addressing The multi-core of the core to be produced has a graded refractive index profile, which is a fu mode and has a distinct effective refractive index for a particular mode. In the vicinity of the core (10) to be addressed, there are cores (4.1 to 4.3) having a graded refractive index distribution, and the effective refractive index of the mode is determined for each of the cores (10) to be addressed. Is selected to match the effective refractive index of the mode. In areas where the insulation is not reduced, a super mode is formed such that the maximum crosstalk observed between any core pair is less than -10 dB (inefficient formation).

  The structure of the multi-core fiber (2) is modified so that in some parts the structure of the hole (6) is crushed, this part being able to efficiently form a supermode on the addressing core and the addressed core. There is enough length. The length of the collapsed portion of the hole (6) is 5 mm, the taper transition region (b) = 2 mm, and the taper ratio is 10%.

  (C) = 5 mm, reduced core insulation is formed as a result of collapse of the holes separating the cores, super mode is formed and crosstalk is increased-addressing at the output of multi-core fiber The ratio of the power present in the addressed core in the form of the addressed mode to the power present in the addressing core in the form of the addressing mode at the input of the multicore fiber is greater than -3 dB. If only one addressing core is excited, the form of the unaddressed mode (depending on the initially excited addressing mode) within the specific addressing core (s) and addressed core (s) The ratio between the power present at the output of the multicore and the power in the form of addressing mode in the addressing core (s) initially excited at the multicore input is less than -14 dB. The power level distribution of each addressed mode appearing at the end of the modified portion is “frozen” and this state is further transported by the unmodified portion of the multicore fiber.

  The single-core fumode fiber (9) at the output end of the multicore fiber (2) is connected with the same or similar characteristics as the addressed core (10) of the multicore fiber (2). Therefore, mode multiplexing is performed using three modes in the single-core fumode fiber (9). Therefore, the above-described coupler configuration of the multi-core fiber whose core insulation is controlled and reduced (reduced) is an element (coupler) that enables an addressing mode in the fu mode fiber.

  Similarly, the signal in the fu mode fiber can be demultiplexed using the coupler according to the present invention-the information transmitted in the fu mode fiber and encoded in a particular mode is individually And can be separated into separate optical fibers. By using couplers in the multiplexer and demultiplexer configuration with connections to the fumode optical fiber, a transmission system using mode multiplexing can be constructed.

The dimensions of diffuser-mode fiber 9: clad diameter d16 = 125 [mu] m; diffuser-mode core (10) - the diameter d17 = 10μm, SiO ₂ doped with 5.8 mole% of GeO ₂
Dimensions of multicore fiber (2):
- Few-mode core (10) - the diameter d17 = 10 [mu] m, _SiO doped with 9 mol% of GeO ₂ 2;
- Core (4.1) - diameter d5.1 = 10μm, _SiO doped with 2 mole% of GeO ₂ 2;
- Core (4.2) - diameter d5.2 = 8μm, _SiO 2 doped with 11.3 mol% of GeO _2;
- Core (4.3) - diameter d5.3 = 10μm, _SiO 2 doped with 6.1 mole% of GeO _2;
- cladding (5) - diameter d6 = 250 [mu] m, _SiO doped with 0 mol% of GeO ₂ 2;
-Lattice constant (Λ) = 16 μm
Size of hole (6): Diameter d7 = 8 μm
Taper parameters:
-Part (b) = 2 mm
-Part (c) = 5 mm
-Diameter d1 = 250 μm
−Taper ratio = 10% (d2 = 225 μm)

  The invention of Example 7 is shown in FIG. 3, FIG. 18, and FIG. In this configuration, the three basic modes of the addressing core address the two higher order modes of the core to be addressed.

  A coupler according to the invention is controlled with a multi-core optical fiber (2) in which the core has an effective refractive index with different modes and one of the cores of the multi-core fiber (2)-the core (12) is birefringent. It is possible to construct an element for change mode addressing. In the vicinity of the addressing core is a single mode core with a wavelength of 1550 nm having a graded refractive index selected to match one effective refractive index of the polarization mode (polarization mode x) in the addressing core (12). There is (4). An input single-core fiber (1) is attached to the multi-core fiber (2) having an insulated core, and a single-core birefringence polarization maintaining fiber (11) is attached to the opposite side of the multi-core fiber. In the part 2), the insulation is reduced by the destruction of the structure of the insulating hole (6) and the tapering of the fiber. The addressing core (12) of the multicore fiber (2) has a graded refractive index, is birefringent, and has a distinct effective refractive index for a particular polarization mode. In the area where the insulation is not reduced, a super mode is formed (inefficient formation) so that the maximum crosstalk observed between any pair of cores is less than -10 dB.

  The structure of the multi-core fiber (2) is modified so that the structure of the hole (6) is crushed at some part. The length of the collapsed portion of the hole (6) is (c) = 3 mm, the taper transition region (b) = 2 mm, and the taper ratio is 20%.

  In the portion of (c) = 5 mm, a reduced (reduced) core insulation is formed as a result of crushing the holes separating the cores, and crosstalk is increased. As a result of the reduced insulation, a supermode is formed and, as a result, crosstalk is increased-at the power of the addressed mode in the form of an addressed mode at the output of the multicore fiber and at the input of the multicore fiber. The ratio to the power present in the addressing core in the form of the addressing mode is greater than -4 dB. Furthermore, the ratio of the power present in the multi-core output in the unaddressed mode form in the addressed core to the power in the initial addressing mode form at the multi-core input is less than -12 dB. The power level distribution of each addressed mode appearing at the end of the modified portion is “frozen” and this state is further transported by the unmodified portion of the multicore fiber.

  After the collapsed hole, the signal propagates through a highly birefringent core where only one propagation mode is substantially excited. An output fiber that maintains polarization with birefringence is connected to a core with high birefringence.

  Therefore, the above coupler structure in the multi-core fiber in which the reduction (reduction) of the core insulation is controlled is an element (coupler) that enables the polarization mode to be addressed, and thus when constructing an optical fiber polarizer. A coupler with the opposite configuration can also be used.

Dimensions of multicore fiber (2):
- Core (4) - the diameter d5 = 8.2 .mu.m, _SiO doped with 3.5 mole% of GeO ₂ 2;
- Core (12) - short axis d18 = 6 [mu] m, major axis d19 = 12.4μm, _SiO 2 doped with 3.5 mole% of GeO _2;
- cladding (5) - diameter d6 = 125 [mu] m, 0 mole% of the doped SiO ₂ (quartz glass) with GeO ₂
-Lattice constant (Λ) = 16 μm
Size of hole (6): Diameter d7 = 10m
Taper parameters:
-Part (b) = 2 mm
-Part (c) = 3 mm
-Diameter d1 = 125 μm
−Taper ratio = 20% (d2 = 100 μm)

  The invention of the eighth embodiment is shown in FIG. 3, FIG. 20, and FIG. In this configuration, the fundamental mode of the core (4) to be addressed addresses the polarization mode of the core (12) to be addressed.

  With the coupler according to the invention, the multicore-core has an effective refractive index with different modes, and two of the cores of the multicore fiber (2)-the core (12.1) and the core (12.2) are birefringent. It is possible to construct a device for controlled addressing comprising a 3-core fiber 2 that is responsive. In the vicinity of the addressed core, there is a graded refractive index selected to match the effective refractive index of the polarization modes in the addressed cores (12.1) and (12.2). There is a single mode core (4) having a wavelength of 1550 nm. An input single-core fiber (1) is attached to the multi-core fiber (2) having an insulated core, and a single-core birefringence polarization maintaining fiber (11) is attached to the opposite side of the multi-core fiber. In the part 2), the insulation is reduced by the destruction of the structure of the insulating hole (6) and the tapering of the fiber. The addressing cores (12.1) and (12.2) of the multicore fiber (2) have a graded refractive index, are birefringent, and have a separate effective refractive index for a particular polarization mode. ing. In the area where the insulation is not reduced, a super mode is formed (inefficient formation) so that the maximum crosstalk observed between any pair of cores is less than -10 dB.

  The structure of the multi-core fiber (2) is modified so that the structure of the hole (6) is crushed at some part. The length of the collapsed portion of the hole (6) is (c) = 5 mm, the taper transition region (b) = 2 mm, and the taper ratio is 10%.

  In the portion of (c) = 5 mm, a reduced (reduced) core insulation is formed as a result of crushing the holes separating the cores, and crosstalk is increased. As a result of the reduced insulation, a supermode is formed and, as a result, crosstalk is increased-at the power of the addressed mode in the form of an addressed mode at the output of the multicore fiber and at the input of the multicore fiber. The ratio to the power present in the addressing core in the form of the addressing mode is greater than -4 dB. Furthermore, the ratio of the power present at the output of the multi-core in the form of unaddressed mode within the particular core being addressed to the power of the form of the initial addressing mode at the input of the multi-core is less than -12 dB. The power level distribution of each addressed mode appearing at the end of the modified portion is “frozen” and this state is further transported by the unmodified portion of the multicore fiber.

  After the collapsed hole, the signal propagates through a highly birefringent core where only one propagation mode is substantially excited. An output fiber that maintains polarization with birefringence is connected to a core with high birefringence.

  Therefore, the above coupler structure in a multi-core fiber in which the reduction (reduction) of core insulation is controlled is an element (coupler) that makes the polarization mode addressable, and thus an optical fiber polarizer that, when constructed, splits the polarization state. . In the opposite configuration, the coupler can be used as a polarization combiner.

Dimensions of multicore fiber (2):
- Core (4) - the diameter d5 = 8.2 .mu.m, _SiO doped with 3.5 mole% of GeO ₂ 2;
- Core (12.1) - minor axis d18.1 = 6μm, the long axis d19.1 = 12.2μm, _SiO 2 doped with 3.5 mole% of GeO _2;
- Core (12.2) - minor axis d18.2 = 6μm, the long axis d19.2 = 12.2μm, _SiO 2 doped with 3.5 mole% of GeO _2;
- cladding (5) - diameter d6 = 125 [mu] m, 0 mole% of the doped SiO ₂ (quartz glass) with GeO ₂
-Lattice constant (Λ) = 16 μm
Size of hole (6): Diameter d7 = 10m
Taper parameters:
-Part (b) = 5 mm
-Part (c) = 5 mm
-Diameter d1 = 125 μm
−Taper ratio = 10% (d2 = 112.5 μm)

  The invention of Embodiment 9 is shown in FIG. 3, FIG. 22, and FIG. In this configuration, the polarization modes of the cores 12.1 and 12.2 in which the three fundamental modes of the addressing core (4) are addressed are addressed.

  With the coupler according to the invention, the construction of an element for addressing a controlled polarization mode with a dual-core optical fiber (2) with a multicore-birefringent core (12.1) and a core (12.2) is possible. It becomes possible. The core is homogeneous. A single-core birefringent polarization maintaining fiber (13) is attached to the multicore fiber (2) having an insulated core, and a single-core birefringent polarization maintaining fiber (11) is attached to the opposite side of the multicore fiber, In the portion of the multi-core optical fiber (2), the insulation is reduced by the destruction of the structure of the insulating hole (6) and the tapering of the fiber.

  Two of the cores of the multicore fiber (2) —the cores (12.1) and (12.2) have different graded refractive indices and are birefringent. In the vicinity of the addressed core, there is a graded refractive index selected to match the effective refractive index of the polarization modes in the addressed cores (12.1) and (12.2). There is a single mode core (4) having a wavelength of 1550 nm. An input single core birefringence polarization maintaining fiber (13) is attached to the multicore fiber (2) having an insulated core, and an output single core birefringence polarization maintenance fiber (11) is attached to the opposite side of the multicore fiber, In the portion of the multi-core optical fiber (2), the insulation is reduced by the destruction of the structure of the insulating hole (6) and the tapering of the fiber. The core of the multi-core fiber (2) has a graded refractive index and a separate effective refractive index for a particular polarization mode. In the area where the insulation is not reduced, a super mode is formed (inefficient formation) so that the maximum crosstalk observed between any pair of cores is less than -10 dB.

    The structure of the multi-core fiber (2) is modified so that the structure of the hole (6) is crushed at some part. The length of the collapsed portion of the hole (6) is (c) = 5 mm, the taper transition region (b) = 2 mm, and the taper ratio is 10%.

  In the portion of (c) = 5 mm, a reduced (reduced) core insulation is formed as a result of crushing the holes separating the cores, and crosstalk is increased. As a result of the reduced insulation, a super mode is formed and, as a result, crosstalk is increased-the power present in the addressed core in the form of an addressed mode in the output multi-core fiber and at the input of the multi-core fiber The ratio to the power present in the addressing core in the form of the addressing mode is greater than -3 dB.

  After the collapsed hole, the signal propagates through a highly birefringent core where only one propagation mode is substantially excited— (x) and (y). The output fiber (11) that maintains the polarization with birefringence is connected to a core having high birefringence.

  Therefore, the above coupler structure in a multi-core fiber in which the reduction (reduction) of core insulation is controlled is an element (coupler) that makes the polarization mode addressable, and thus when constructing a fiber optical coupler (splitter) polarization maintaining. In addition, the signal existing at the beginning of the core (12.1) is divided into the cores (12.1) and (12.2), and the polarization state is maintained. In the opposite configuration, the coupler can be used as a polarization combiner.

Dimensions of multicore fiber (2):
- Core (12.1) - minor axis d18.1 = 6μm, the long axis d19.1 = 12.4μm, _SiO 2 doped with 3.5 mole% of GeO _2;
- Core (12.2) - minor axis d18.2 = 6μm, the long axis d19.2 = 12.4μm, _SiO 2 doped with 3.5 mole% of GeO _2;
- cladding (5) - diameter d6 = 125 [mu] m, 0 mole% of the doped SiO ₂ (quartz glass) with GeO ₂
-Lattice constant (Λ) = 16 μm
Size of hole (6): Diameter d7 = 10m
Taper parameters:
-Part (b) = 5 mm
-Part (c) = 5 mm
-Diameter d1 = 125 μm
−Taper ratio = 10% (d2 = 112.5 μm)

  The invention of the tenth embodiment is shown in FIG. 3, FIG. 24 and FIG. In this configuration, the core 12.1 to be addressed addresses the polarization mode of the core 12.2 to be addressed.

  The coupler according to the invention allows the construction of a device for controlled addressing comprising a multi-core optical fiber (2) having a core insulated with a reduced area of refractive index (6) in the form of air-filled holes become. One of the cores (4.3) is a single mode core at a wavelength of 1550 nm and has a graded refractive index profile, and the second core (10) is a fumode core, which is also graded refractive. Has a rate distribution. A dual-core fiber (2) with a multi-core-insulated core is fitted with two input single-core fibers (1) and (9), and on the opposite side of the multi-core optical fiber are two output single-core fibers (1 ) And (9) are attached, and in the portion of the multi-core optical fiber (2), the insulation is reduced by crushing the structure of the insulating hole (6). The distance between the microstructure elements (hole and core) is equal to the lattice constant (Λ), the diameter of the insulating hole is 10 μm, the core (10) -the multi-core to which the core is addressed has a graded refractive index profile, It is a fu mode and has a distinct effective refractive index of a specific mode. In the vicinity of the addressed core (10) is an addressing core (4.3) having a graded refractive index, and the effective refractive index of the mode is the mode (first order) in the addressed core (10). 3 higher order modes) are selected to match one effective refractive index. Since the effective refractive index of the mode of the core (4.3) and one of the modes of the core (10) are matched, a super mode is formed before the reduction of the insulation, and thus in the portion where the insulation is reduced. The Therefore, the mode of the core (4.3) addresses the mode of the core (10), and the mode of the core (10) addresses the mode of the core (4.3). Therefore, there is a possibility of realizing an add-drop multiplexer / demultiplexer. Both cores (4.3) and (10) are addressing cores as well as addressing cores.

  In the area where the insulation is not reduced, a super mode is formed (inefficient formation) so that the maximum crosstalk observed between any pair of cores is less than -10 dB.

  The structure of the multi-core fiber (2) consists in part of the structure of the hole (6) long enough to form a supermode on the addressing core and the addressed cores (10) and (4.3). Is fixed to be crushed. The length of the collapsed portion of the hole (6) is (c) = 5 mm, the taper transition region (b) = 2 mm, and the taper ratio is 10%.

  (C) = 5 mm portion, reduced (reduced) core insulation is formed as a result of the holes separating the cores being crushed, and crosstalk is increased--reduced insulation results in formation of a super mode and crosstalk -The ratio of the power present in the addressed core in the form of the addressed mode in the output multicore fiber to the power present in the addressing core in the form of the addressing mode at the input of the multicore fiber is- Greater than 3 dB. If only one addressing core is excited, the form of the unaddressed mode (depending on the initially excited addressing mode) within the specific addressing core (s) and addressed core (s) The ratio of the power present at the multi-core output to the power in the form of the addressing mode in the initially excited addressing core at the multi-core input is less than -14 dB. The power level distribution of each addressed mode appearing at the end of the modified portion is “frozen” and this state is further transported by the unmodified portion of the multicore fiber.

The dimensions of diffuser-mode fiber (9): clad diameter d16 = 125 [mu] m, the core diameter d17 = 20 [mu] m, _SiO doped with 5.8 mole% of GeO ₂ 2;
Multi-core fiber 2 dimensions:
- Few-mode core (10) - the diameter d17 = 20 [mu] m, _SiO doped with 5.8 mole% of GeO ₂ 2;
- Core (4.3) - diameter d5.3 = 6.4μm, _SiO doped with 5.8 mole% of GeO ₂ 2;
- cladding (5) - diameter d6 = 250 [mu] m, 0 mol% of SiO ₂ doped with GeO ₂ (quartz glass)
-Lattice constant (Λ) = 20 μm
Size of hole (6): Diameter d7 = 10 μm
Taper parameters:
-Part (b) = 2 mm
-Part (c) = 5 mm
-Diameter d1 = 250 μm
−Taper ratio = 10% (d2 = 225 μm)

  The invention of this embodiment is shown in FIG. 3, FIG. 26 and FIG. In this configuration (multiplexer), the mode of core 4.3 addresses the third higher order mode of the core, and the third higher order mode from core 10 addresses the mode of core 4.3. Furthermore, other modes propagate to the fu mode core by initial excitation. In this configuration, it is imperative to add additional signals to the core 10 in which other modes propagate, and one signal can be dropped from other signals propagating through this core. The embodiment relates to the implementation of add-drop multiplexing by adding / removing one of the channels to / from the signal propagating through one core.

The following is the invention described at the beginning of the application.
<Claim 1>
A fiber optic coupler comprising a multi-core optical fiber having an insulated core, wherein the core insulation is configured as a zone manifestation characterized by a reduced refractive index in the vicinity of the core, comprising: N output optical fibers Including at least one input optical fiber bonded to at least an N-core multi-core optical fiber having a bonded, insulated core, and reducing the size of the reduced refractive index zone in the vicinity of the core A fiber optic coupler characterized in that the insulation of the fiber is reduced in at least one part of the multi-core optical fiber.
<Claim 2>
The fiber optic coupler according to claim 1, wherein the component multi-core optical fiber has a core having air-assisted insulation.
<Claim 3>
3. The fiber optic coupler according to claim 1, wherein at least one segment of the multi-core optical fiber is tapered at a certain portion, and the hole is crushed.
<Claim 4>
4. The fiber optical coupler according to claim 1, wherein at least one piece of the multi-core optical fiber and its hole are crushed without being tapered.
<Claim 5>
5. The fiber optic coupler according to claim 1, wherein an optical fiber is used that guarantees the occurrence of crosstalk with a core insulation level of 10 dB or less.
<Claim 6>
6. The fiber optic coupler according to claim 1 or 2, or 3 or 4 or 5, wherein at least two single optical fibers are connected to both sides of a multi-core optical fiber having an insulated core.
<Claim 7>
The length of the taper is greater than 300 μm, and the designed signal splitting level depends on the length and degree of tapering and / or the degree of fracture of the holes, characterized in that Or the fiber optical coupler of 6.
<Claim 8>
8. The fiber optic coupler according to claim 1 or 2, or 3 or 4, or 5 or 6 or 7, wherein the power division is equal.
<Claim 9>
9. A fiber according to claim 1 or 2 or 3 or 4 or 5 or 6 or 7 or 8 characterized in that the taper ratio is 0 to 95%, said taper ratio being regarded as the reduction ratio of the fiber cross section. Optical coupler.
<Claim 10>
10. The fiber optic coupler according to claim 1, wherein the single optical fiber connected to the multi-core optical fiber is a standard single mode optical fiber. .
<Claim 11>
The single optical fibers connected to the multi-core optical fibers are standard single-mode optical fibers that are etched and / or tapered so that their cores are aligned with the cores of the multi-core optical fibers. Item 11. The fiber optical coupler according to item 1 or 2 or 3 or 4 or 5 or 6 or 7 or 8 or 9 or 10.
<Claim 12>
12. The fiber light according to claim 1, wherein the single optical fiber connected to the multi-core optical fiber is arranged in a narrow tube. Coupler.
<Claim 13>
The single optical fiber connected to the multi-core optical fiber is connected by fusion splicing, or the optical fiber according to claim 1, 2 or 3 or 4 or 5 or 6 or 7 or 8 or 9 or 10 or 11 or 12. Fiber optic coupler.
<Claim 14>
At least one core of the multi-core fiber is an addressed core, so that it is multi-mode (fu mode) and / or birefringent at the wavelength used, at least one core is the addressing core Yes, at least one at least single-core input fiber is connected to the multi-core fiber, and at least one at least single-core output fiber is attached to the opposite side of the multi-core fiber, and the core insulation is reduced in at least one part of the multi-core fiber The fiber optical coupler according to claim 1, wherein the power existing in the core addressed by the output of the multicore fiber is larger than the power at the input of the multicore fiber.
<Claim 15>
15. The fiber optic coupler according to claim 14, wherein the insulating structure has the form of a zone with a reduced index of refraction selected from holes filled with air or gas, or solid or liquid.
<Claim 16>
16. A fiber optic coupler according to claim 14 or 15, wherein the addressing core or cores are in single mode at the wavelength used.
<Claim 17>
17. A fiber optic coupler according to claim 14 or 16, characterized in that the one or more cores to be addressed are birefringent at the wavelength used and / or are multimode (fue mode).
<Claim 18>
18. The fiber optic coupler according to claim 14, 15 or 16 or 17, wherein the addressing core has a refractive index of different modes.
<Claim 19>
19. The fiber optic coupler according to claim 14, 15 or 16, or 17 or 18, wherein the addressed core and the addressing cord have the same refractive index of a particular mode.
<Claim 20>
The ratio of the power present in the addressed core in the form of the addressed mode at the output of the multicore fiber to the power present in the addressing core in the form of the addressing mode at the input of the multicore fiber is -5 dB. The fiber optic coupler according to claim 14, 15, 16, 17, 18, or 19.
<Claim 21>
If only one addressing core is excited, the power present at the output of the multi-core in the form of an unaddressed mode (depending on the initially excited addressing mode) of the specific addressing core or cores and addressed cores And the power at the input of the multi-core in the form of an addressing mode in the initially excited addressing core is less than -10 dB, 14 or 15 or 16 or 17 or 18 or 19 Or the fiber optic coupler of 20.
<Claim 22>
21. The length of the fiber modification as a taper of the fiber and / or breakage of its hole is equal to the length used of the multi-core fiber, 21 or 16 or 17 or 18 or 19 or 20 Or the fiber optical coupler of 21.
<Claim 23>
23. The fiber optical coupler according to claim 1, wherein the zone having a reduced refractive index is filled with a fiber cladding, and the entire fiber cladding serves as a refractive index reducing zone.
<Claim 24>
24. The one or more fibers connected to a multicore fiber are single mode and / or birefringent and / or multimode (fumode) fibers. Fiber optic coupler.
<Claim 25>
25. The fiber optic coupler according to claim 1, wherein the one or more fibers connected to the multi-core fiber have parameters corresponding to the parameters of the core of the multi-core fiber.
<Claim 26>
The deconfiguration (demultiplexing mode) in which the role of addressing one or more cores is played by one or more cores to be addressed and the role of one or more cores to be addressed is played by the addressing cores The fiber optic coupler according to any one of claims 1 to 25, wherein the fiber optic coupler can be used in any of the above.
<Claim 27>
The coupling between the cores, and thus the splitting of the signal (its power and / or wavelength), can be achieved by taper length (extension) and / or tension, in particular using a mechanical device that winds the fiber around a piezoelectric structure or deforms the fiber. 27. The fiber optic coupler according to claim 1, which can be changed by changing (compression, bending, twisting) and / or temperature.

Claims (20)

  A fiber optic coupler comprising a multi-core optical fiber having an insulated core, the core insulation comprising a zone manifestation characterized by a reduced refractive index in the vicinity of the core, wherein at least one is at most N N cores with an insulated core (4) bonded to a plurality of output optical fibers (1) or (9), at least one with at least dual core and even at least one bonded to a multicore optical fiber (2) Also has N optical fibers (1) or (9), and by reducing the size of the reduced refractive index zone in the vicinity of the core (4), the core insulation is at least one of the multi-core optical fibers (2). A fiber optic coupler characterized by being reduced in two parts.   2. The fiber optic coupler according to claim 1, wherein the component multicore optical fiber (2) has a core (4) with insulation in the form of air holes (6).   3. The fiber optic coupler according to claim 1 or 2, characterized in that at least one segment of the multi-core optical fiber (2) is tapered at a certain portion and the hole (6) is crushed.   3. The fiber optic coupler according to claim 1, wherein at least one piece of the multi-core optical fiber (2) and its hole (6) are crushed without additional tapering.   An optical fiber is used in which the insulation of the core (4) before and after the part with reduced core insulation guarantees the occurrence of crosstalk with a level of less than -10 dB. Or the fiber optic coupler of 4.   The length of the fiber part in which the core insulation is reduced is greater than 300 μm, and the designed signal splitting level depends on this length and taper ratio and / or the breakdown level of the hole (6). The fiber optical coupler according to 1, 2, 3, 4 or 5.   The fiber optic coupler according to claim 1, 2, 3, 4, 5, or 6, wherein the taper ratio is 0 to 95%, and the taper ratio is configured by a reduction ratio of the fiber cross section (6). .   The single optical fiber (1) connected to the multi-core optical fiber (2) is a standard single-mode optical fiber according to claim 1 or 2 or 3 or 4 or 5 or 6 or 7 Fiber optical coupler.   At least one of the cores of an N-core, at least dual-co, and even multi-core optical fiber (2) is an addressed core in which one or more modes are excited and birefringent at the wavelength used Addressing used to excite one or more specific modes of one or more cores in which the one or more modes are addressed A core that is birefringent and / or single mode or multimode or fumode at the wavelengths used, and at least one N-core fiber (2) and at least N at least single-core input fibers ( 1) or (9) or (13), and the opposite side of the N-core fiber (2) is at least one N at least single-core output fibers (1) or (9) or (11) are mounted, the core insulation is reduced in at least one part of the N-core fiber (2), and the multi-core fiber (2) 9. The fiber optic coupler according to claim 1, wherein the power present in the core addressed at an output of is greater than at the input of the multi-core fiber (2).   10. The fiber optic coupler according to claim 9, wherein the insulating structure has the form of a zone having a reduced refractive index selected from air (6) filled with air or gas or solid or liquid. .   The fiber optic coupler according to claim 9 or 10, wherein effective refractive indexes of a plurality of core modes to be addressed are different.   12. A fiber optic coupler according to claim 9, 10 or 11, characterized in that the addressed core (10) and the addressing core have the same refractive index in a particular mode.   The ratio of the power present in the core addressed in the form of the addressed mode at the output of the multicore fiber (2) to the power present in the core addressed in the form of the addressing mode at the input of the multicore fiber is 13. The fiber optic coupler according to claim 9, 10 or 11 or 12, characterized in that it is greater than -5 dB.   If only one addressing core is excited, the multi-core is in the form of a mode that is not addressed by the initial addressed addressing mode in the specific addressing core or cores and the addressed core or cores. A ratio between the power present at the output and the power at the input of the multi-core in the form of an addressing mode in the initially excited addressing core is less than -10 dB. Or a fiber optic coupler according to 13;   12. The length of the fiber modification as a taper of the fiber and / or breakage of its hole (6) is equal to the length used of the multi-core fiber (2). Or the fiber optical coupler of 12 or 13 or 14.   16. A zone having a reduced refractive index is filled with a fiber cladding (5) material, and the entire fiber cladding serves as a zone having a reduced refractive index. Fiber optic coupler.   One or more fibers (1) or (9) or (13) connected to a multi-core fiber (2) may be single mode (1) and / or birefringent (13) and / or multimode (9 ) Or a fumode (9) fiber.   The one or more fibers (1) or (9) or (13) connected to the multi-core fiber (2) have a core refractive index profile corresponding to the core refractive index profile of the multi-core fiber. The fiber optic coupler according to claim 1, wherein the fiber optic coupler is a fiber optic coupler.   Mode in which the role of addressing one or more cores is played by one or more cores being addressed, and the role of one or more cores being addressed is played by one or more cores addressing The fiber optic coupler according to claim 1, wherein the fiber optic coupler can be used in a reverse configuration in which is demultiplexed.   The coupling between the cores, and thus the signal splitting, can be achieved by stretching and / or compressing and / or bending and / or twisting, in particular using a mechanical device that winds the fiber into a piezoelectric structure or deforms the fiber. The fiber optical coupler according to claim 1, wherein the fiber optical coupler can be changed by changing the taper length according to temperature.

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