JP6961487B2 - Fiber optic coupler - Google Patents

Description

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

The power coupler is one of the basic components used in a communication line based on the use of optical fiber. To develop higher data transmission densities, the telecommunications market must take into account the requirements of data recipients with a focus on improving data transmission densities, improving functionality and reducing the cost of deploying new systems. .. The purpose of a fiber optical coupler is to transmit power from one or more input optical fibers to one or more output optical fibers. The coupler can be implemented in any input / output configuration. The most common types of couplers include x-type couplers (2 inputs and 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 was necessary to manufacture couplers with a larger number of channels. If desired, the coupler can have any number of inputs and outputs, while the main constraint is the ability to manufacture the coupler. In an extreme case, 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. With N inputs and one output, the coupler becomes an optical signal combiner.

Properly integrated power splitters and combiners are used to ensure full deployment of state-of-the-art access networks, especially those defined as FFTx networks (fibers to the x, eg FTTH-fibers to the home). is necessary.

The FTTx network is usually constructed by PON (Passive Optical Network) technology. There is a point-to-multipoint network that runs in a logical star topology. The physical topology depends primarily on the distribution of subscribers: for single-family homes, the most common topology is the bus network, while for multi-family homes, the most common solution is the tree. Topology. In each case, the central point is composed of a distributor, that is, an optical coupler that divides a signal from an OLT (optical network unit) into a network terminal with a recipient, a so-called ONT (optical network terminal device).

The latest commercial signal coupling elements used in telecommunications are generally manufactured using two technologies: fiber optic fusion (FBT-fused bicone (Bionical) taper) and planar technology (PLC-planar lightwave circuitry). In the case of bus network technology, the optical coupler utilized is usually implemented in FBT technology. For tree network topologies that require a large number of output ports, the primary solution utilized is the PLC coupler. Is.

The FBT coupler is formed by arranging two optical fibers adjacent to each other, then fusing them together and tapering them to form a single waveguide. In this structure, properly adjacent cores can no longer be treated as separate communication channels. The signal entering one of the arms of the coupler passes through a tapered area, where the size of the optical fiber is significantly reduced, causing the core to lose its ability to transmit light, so light is conducted by the entire glass surface and air. Plays the role of clad. As the tapered optical fiber expands, the core, which also increases in diameter, regains its guiding capacity. In such an arrangement, Maxwell's equations are solved for the entire structure, resulting in a so-called supermode in which some or all cores propagate simultaneously. Depending on the configuration, light propagation in such a structure can be used to construct a power combiner or splitter.

A coupler manufacturing process through fusion by FBT technology is described in US Pat. No. 4,550,974, a patent document describing the couplers and methods of manufacturing them. The coupler presented herein is a symmetric 2x2 coupler, but asymmetric couplers, i.e. couplers with non-uniform power splits, can also be manufactured. Such a coupler can operate in a 1x2 power splitter configuration using only one of the plurality of inputs. Its features are high resistance to changes in the conditions of the external network, low insertion loss, and slight back reflection. One of the drawbacks of such a coupler 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 (4-128), ensuring the small dimensions of the product itself and high operational stability over the 1260 to 1650 nm spectral range. Can be manufactured. Such a structure is particularly utilized for integrated optics. A feature of a device having such a structure is that the total loss reaches several decibels because the mode conversion needs to be performed, so that the loss is relatively large and the internal loss is large. In addition, the technology for assembling and connecting integrated optics and optical fibers requires sophisticated and costly methods. The structure of the PLC coupler and the method for manufacturing the PLC coupler are described in particular in Patent Document, US Pat. No. 5,745,619, and US Pat. No. 2,3001,289A1.

The basic parameters of optical couplers currently in use are major obstacles to the widespread use of access networks, especially access networks defined as FTT networks that presuppose the use of optical fibers used in all transmission stages. Therefore, in particular, the purpose of the invention consisting of a fiber optical coupler utilizing a microstructured multi-core optical fiber used as a power combiner and a splitter is to develop a device that serves as an element that guarantees optimum power for an arbitrary 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 fiber, which is more advantageous than planar technology, which is difficult to integrate into optical fiber based telecommunications systems. Depending on the manufacturing technique utilized, the device according to the invention keeps the loss low and guarantees the required power split. Two criteria-specific power splits, and low losses during such splits, are key points of 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 approached to zero. In addition, the above devices are available 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, as well as an MxM coupler. In addition, being able to operate as a splitter / combiner / coupler allows the device to be used as an optical switch.

With the invention of photonic crystal fibers, which are also called microstructure fibers, the possibility of mode molding in optical fibers has greatly expanded. In the case of microstructured fibers, differential geometry (geometric differences) involving the arrangement of structural vacancies and manipulation of properties produces fiber properties that could not be achieved using conventional optical fibers. can do. These properties include, for example, single-mode operation over a very wide spectral range, high birefringence, high pressure sensitivity, elongation and many other properties. The effect of vacancies on the characteristics of the mode is small for light propagation without the influence of external factors, but additional external factors can significantly improve fiber performance. An example of such an application could be, for example, a low bending loss fiber containing a core in which the optical fiber is surrounded by vacancies. Such an optical fiber is presented in a paper entitled "Low Bending Loss Single Mode Pore Assist Fiber" such as Toshiki Taro published in SEI Technical Review 75 (2012). The advantages of this type of fiber become apparent when bent-in the case of fiber optics whose core is not surrounded by vacancies, bending causes considerable loss. In the case of pore-assisted insulation, there is a possibility of "mode outflow", and the index of refraction pitch of the large structure (the holes can be filled with various substances, but the index of refraction in the hole region is the index of refraction of air. Mode power emission to the cladding is practically impossible because of the occurrence). Therefore, the presence of pores does not have a significant effect on properties such as dispersion and attenuation because these positions are relatively far from the core, but it can affect the characteristics of propagation due to external factors. ..

The pores of the microstructured optical fiber can also be used to construct a multi-core optical fiber with little involvement in propagation (a large involvement is seen in the case of LMA-8 optical fibers). Due to the vacancies around the cores, power propagation between specific cores is virtually eliminated-the so-called crosstalk phenomenon does not occur. In addition, the holes can insulate the cores, which means that the propagation of power within each core is virtually independent. Cores can also be surrounded by holes so that modes cannot be assigned to specific cores-such cores are called "coupling" cores, and supermode propagates the structure. Whether it is an insulated core or a combined 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 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 so on. Therefore, it is possible to change the propagation state after manufacturing the optical fiber.

Although vacancies are well known, the controlled use of this phenomenon to achieve fiber optic coupling between the cores of a particular multi-core optical fiber has not yet been developed.

For example, the patent document, US Pat. No. 6,631,234, 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 crushing phenomenon is described as "weakening and fracture of the differential index between the clad and the core". In addition, the birefringence of the optical fiber can be modified by controlling the size of the pores and changing the diameter of the optical fiber.

Pore fracture of a photonic crystal fiber can also be used to connect an optical fiber having a fine structure. The vacancy fracture phenomenon has been regarded as a problem because it causes connection loss. This phenomenon can be utilized or eliminated (eg by gradual vacancy destruction). However, in most cases, the connection technology is considered to be for single-core photonic crystal fibers.

For example, in the patent document, U.S. Patent Application No. 20080037939, the inventor tapers a single-core photonic crystal fiber that utilizes stepwise vacancies to reduce junction loss (connection loss). Is presented.

On the other hand, Patent Application No. 20060067632 is a single-core photonic crystal characterized by a small core, which focuses on pore fracture with as few connection execution methods as possible in order to minimize loss as much as possible. A fiber connection method is presented.

A method of connecting a single-core photonic crystal fiber is also described in US Pat. No. 7,609,928 B2, a patent document that clearly states that hole fracture is the cause of loss.

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

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

A similar solution in which the contiguous zones are fused and clad mode and core mode are implemented in two interferometers is described in the patent document, European Patent No. 19396559 B1.

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

One of the selective mode excitation methods uses a phase plate or SLM. In each case, the light beam (usually the basic mode) hits a transparent element with a predetermined index of refraction distribution that results in a particular higher order mode at a distance from the back of the plate as a result of the topological structure. Similarly, an SLM that introduces the appropriate phase delay added can be used. SLMs are extremely versatile in use because phase delays can be programmed when using SLMs, resulting in higher order modes of any shape. Both of these methods use bulk optics at the optical beam inputs and outputs of fumode fibers. As a result, unfortunately, the size of this type of device, which is often composed of several elements, increases. At the same time, using more precise devices is more expensive. This method seems to be the simplest, but it is costly. R. A paper by Ryf et al., "Mode divisional multiplexing larger than 96 km using coherent 6x6 MIMO processing" (2012, Lightwave Technology. Journal No. 30), is a multiplexing using fumode multiplexing of transmission by six independent channels. Presenting transmission. The transmission rate achieved 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 in fumode optical fiber where the element that shapes the beam into the desired mode was SLM. In fiber optic networks, the use of bulk optics leads to the inevitable introduction loss associated with transmission from the bulk optics to the fiber optics.

Another method, called a "photonic lantern", is based on the tapering of some single core fibers with the required parameters. These parameters (core size, core index of refraction) are generally different until the core stops the independent light guide, resulting in a reduced index of refraction and a glass outer tube that acts as a fiber clad. A fumode fiber having the above is formed. By appropriately selecting the parameters of the single core fiber at the input, a particular mode can be obtained at the output. At the same time, it is possible to stimulate another mode at the output, depending on which input the single core fiber signal is introduced into. The advantage of this method is that it uses very low loss and uses fiber optic technology (full fiber type). However, the challenge is to keep crosstalk between modes low. Currently, transmissions using this type of multiplexer have a high degree of coupling between modes during multiplexing, 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. The paper "Fiber LPG Mode Converters and Mode Selection for Multimode SDM Technology" by Giles et al. (2012, IEEE Photonic Technology Papers) is a concept of such devices based on long-period fiber grating and its test methods. Is presented. Another method of using 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. D. Love, N.M. In Riesen's paper "Single-Number-and Multimode Y Junctions" (2012, Lightwave Technique, Journal No. 30, pp. 304-309), this type of asymmetry is used to stimulate higher-order modes. The simulation results of the structure are presented.

In particular, there is an example of a paper by Sung Hyok Chang et al., "Models using all-fiber multiplexer mode based on mode selection couplers and wavelength division multiplexing transmission" (2015, Opti. Express, No. 23), which are three. It uses fiber couplers to multiplex and demultiplex modes, and the solution relies on a cascade of traditional 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, European Patent No. 2336813 relates to a multi-core fiber for transmission using mode multiplexing without selective, particularly precise addressing modes. The modes in the fiber are grouped together and the core structure has no insulation. The description of the invention only mentions the possibility of multiplexing and demultiplexing, but does not disclose how to perform this operation. Indirectly from the description and the contents of the drawings, it can be concluded that this operation is performed by the planar phase plate or by analogs thereof. Therefore, by using only fiber optics, multiplexing and demultiplexing are not included in the illustrated embodiments, and additional components suitable for the purposes of the invention need to be used.

Similarly, the solution, European Patent No. 2706387, applies to optical fibers 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 fiber dedicated to transmission.

Devices that allow signal multiplexing are typically devices based on bulk optics, such as those disclosed in US Pat. No. 6,332,050 for the design of bulk multiplexers. These types of solutions are expensive and inefficient, which was the starting point for the study of the present invention.

On the other hand, U.S. Patent No. 2013309627 relates to the use of fibers with coupled cores for transmission based on mode multiplexing, but adds to how addressing modes are performed. It is not disclosed what seems to be necessary based on the explanation of the experimental study in.

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

Well-known solutions are characterized by enormous complexity, among other things. Therefore, an object of the present invention is to provide an element that eliminates the drawbacks of prior art, which is problematic in controlling which mode is stimulated to what extent (synonymous with excitation, addressing), and by using it, a mode signal can be obtained. To be able to do it efficiently and independently. By using the present invention, transmission can be realized by using several modes (mode multiplexing) in one optical fiber. It is also possible to realize an add-drop multiplexer by using the present invention. In addition, an object of the present invention has been to develop the entire structure with an optical fiber technique capable of avoiding the junction of the planar / bulk optical system and the optical fiber. The present invention allows addressing to modes, i.e., basic mode, higher order mode and polarization modes. The polarization mode addressing can be effectively utilized, among other things, in the construction of optical fiber polarizers, optical fiber polarizing splitters (splitters), and fiber optical couplers that maintain polarization. The configuration of such devices is also in demand in the market.

The power coupler of the present invention enables effective optical power coupling by utilizing controlled hole crushing of a multi-core optical fiber structure. A usefully insulated multi-core optical fiber is used as the basic medium, whereas the insulated core is configured as a crosstalk core between each other at -10 dB or less, which is It is ensured by creating a region near the core that is characterized by a low index of refraction compared to the index of refraction of the coating. In an advantageous embodiment, the zone with reduced index of refraction preferably takes the form of air-filled pores. Such holes minimize crosstalk and their effect on signal propagation parameters (loss, variance) is beneficially small. In addition, the holes allow light to enter the coupler without theoretically causing any loss.

In the basic configuration of the present invention, the optical fiber according to the present 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. Including a multi-core optical fiber connected to two single optical fibers, the optical fiber can be placed in a thin tube, but etched and / / to align these cores with the core of the multi-core optical fiber. Alternatively, it can be tapered, at least one piece of the multi-core optical fiber is tapered to a cross section of 300 μm or greater, and / or the holes in this cross section are crushed. On the other hand, the power is distributed so that the signal from a single optical fiber passes through one of the cores of a microstructured multi-core optical fiber, preferably the central core, and the signal is a microstructured multi-core due to the insulation of the core. The holes in the fiber optic are broken and / or pass through this core to the tapered region. In microstructured multi-core fiber optic holes where holes are broken and / or tapered regions, the parameters of the hole tapering and / or crushing process are appropriately selected so that they can be performed, for example, preferably with a fusion splicer. By increasing the crosstalk between the cores, the insulation of the cores is reduced in a controlled manner, as can be done in. The length of the multi-core fiber optic portion outside the waist region of the taper and the transition region and / or the fracture region of the hole does not significantly affect the coupler performance and effective power splitting.

In the region where the holes of the microstructured multi-core optical fiber are broken and / or tapered, the core is not insulated and a super mode occurs. Thus, by reducing core insulation as a result of hole fracture and / or bringing the cores closer together in the case of tapers, and by bringing the fused cores together (increased crosstalk of a particular core). ) Therefore, the optical fiber shifts from the operation of the insulated core to the operation of the 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 greater, and / or the holes in the tapered portion are crushed, and the taper length and taper ratio and / or the level of crushing determine the degree of power division. On the other hand, it is possible to find the taper length and taper ratio and / or the level of hole crushing that favorably equalizes the power split across all cores.

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

Arbitrary MxN splitting can be achieved depending on the design of the microstructured multi-core optical fiber. It is not necessary to completely crush the core to achieve different types of effects. In addition, various divisions into specific cores can be performed by introducing external interactions due to temperature, stress (elongation, compression, torsion, bending, etc.), pressure, etc. The design of multi-core fibers directly affects power splitting as a result of tapering and / or hole filling.

In another embodiment, the fiber optic coupler according to the invention preferably has at least one input optical fiber in single mode and N output optical fibers, and N cores with at least N cores insulated. Includes output optical fiber.

The signal propagating through standard single-mode optical fiber (s) is sent to a multi-core microstructure optical fiber.

The input optical fiber (s) are connected to a multi-core fiber. After passing through the multi-core optical fiber, the signal further enters the taper region and / or the taper region (taper transition region, then the waist region of the taper) and / or the perforation region without perforation. Propagate (s).

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

The division can be adjusted by selecting the diameter of the reduced hole according to the desired power division and selecting the length of the tapered portion (both the tapered transition region and the tapered waist region) and the tapered waist ratio. There is sex. In this fiber optic design, there is a combination of parameters that allows even division of power. The fixation of the power split obtained at the taper section is due to the "freeze" of the mode structure in the passage from the transition section to the section where the core is insulated. The low loss achieved in the present invention is the result of the normal stimulation of supermode performed by the characteristic tapering and / or hole crushing of multi-core fibers. Filling the connections creates a device that acts as a splitter, but usually results in higher losses.

The device according to the invention can also be used as follows. For example, if two wavelengths propagate through an input fiber optic, each of them has a different path, each of which is followed by a completely multi-core fiber optic, especially one of two cores of a dual fiber. Located in one. Therefore, the tapering and / or hole-filling parameters can be selected so that the two wavelengths propagating through the input fiber can be successfully separated into separate cores of the multi-core fiber and into the output fiber optic. The same principle as the principle of separating wavelengths into specific cores can be applied to a large number of cores of two or more cores shown in this example, and to a larger number of wavelengths.

In an advantageous embodiment of the invention, the signal is collected from only one output for a particular application. Such a situation occurs, for example, when certain wavelengths must be filtered rather than simply separated. In this case, the operating principle of the device does not change, but the purpose of the element changes. When filtering wavelengths, one or several output optical fibers may be used, the remaining fibers may be left unused, or one fiber may be connected to the output. Connecting one fiber to the output is advantageous from a technical point of view. Effective wavelengths can also be filtered from the spectrum by applying variable taper parameters to taper adapters connected in series.

Tapered parameters can also be applied 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 in the optical cavity for adjusting the Q factor of the optical cavity (operation as a Q switch).

The above coupler operating principle can be usefully inverted as follows. A beam of an optical signal can be incident on an optical fiber connected to a multi-core fiber having an insulated core. In the non-tapered section, propagation does not change the characteristics of propagation taking place in the input fiber optic. In the tapered and / or hole-filling region, propagation shifts from the behavior of the insulated core to the behavior of the coupled core. A super mode is generated, so that the independently traveling signals merge at this point. At least one single core optical fiber is connected to the multi-core optical fiber. Thus, the merging signal from the input core propagates through the output light (s) fiber at this point with appropriate power loss. Therefore, 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 are referred to below as combiners. The uses of this type of configuration are as follows. When different wavelengths propagate through each fiber, including the input fiber optics, a mixed signal is obtained at the output of the output fiber optics (s). Signals with several wavelengths propagate through one optical fiber.

In another embodiment, the coupler according to the invention allows the construction of an element for a controlled addressing mode, which includes a multi-core optical fiber that is insulated by a zone (space) with a reduced index of refraction but has a core. .. Preferably, at least one core of the multi-core optical fiber is fumode, or birefringent (with separated polarization modes), which modes can be independently addressed (synonymous with stimulation, excitation, multiplexing). Means. This is because each core of the addressing core and the addressing core is surrounded by an insulating structure that insulates one core from the other core, especially when 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 pores can be filled with a fiber clad material, whereby the entire clad 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 maximum crosstalk observed between any core pairs is less than -10 dB.

The core to be addressed, or the multiplexed core (one of the modes is addressing / multiplexing), is a fumode and / or birefringent core and has a distinct effective index of refraction of a particular mode. Birefringence of the core is achieved by any well-known method, such as the ellipticity of the core or the stress state 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 wavelength used. As these terms are used synonymously throughout the patent, there are no well-defined differences between multimode and fumode fibers in the literature.

In the vicinity of the core to be addressed, a multiplexing having an effective index of refraction that matches at least one, preferably a single mode of the addressing core, or one of the modes in the addressing core. There are cores (cores in which a particular mode is used to excite / address a particular mode within the core to be addressed / multiplexed). "Stimulation / excitation of a particular mode" effectively forms a supermode on the core conditioned by adjusting the effective index of refraction of the mode, considering its addressing and thus the core separately (actually observing crosstalk). ) Means that it is possible. After reducing the insulation, the cores are coupled, where the super mode produced by both cores becomes a problem, rather than the individual modes already.

There are two roles in choosing the effective index of refraction of the mode so that each core has a separate index of refraction and the other cores have a regulated effective index of refraction. It firstly reduces crosstalk between the addressing cores (inefficient formation of supermodes due to the separation of the effective index of each mode pair) and secondly, the cores addressing and the cores addressing by phase matching. Allows selective crosstalk between and (efficient formation of supermode). Various forming capabilities of supermode within areas of reduced insulation are made possible by selecting the index of refraction of the mode within the structure with the insulated core-in certain modes the index of refraction is close. The more efficient supermodes are formed by them, and therefore in the form of addressing modes (basic mode, higher order mode, polarization mode) to the power present in the core addressing in the form of addressing mode. The power that exists in the core increases.

A multi-core fiber of at least a dual-core fiber with an insulated core is connected to at least one, at least a single-core input fiber, with at least one, at least a single-core output fiber attached to the opposite side of the multi-core fiber, for multi-core optical. The input and output fibers attached to the fibers can be placed in tubules and their cores can be etched and / or tapered to preferably align with the cores of the multi-core fiber (fan-in-fan). Out element type). Within at least one fragment of the multi-core fiber, the insulation of the core is reduced (reduced) by reducing (reducing) the size of the reduced refractive index zones near the core and / or by crushing their structure. Will be done. In regions where core insulation could be reduced, supermodes are formed on specific addressing cores (s) and / or cores to be addressed (s). The ratio of the power present in the core addressed in the form of addressing mode at the output of the multi-core fiber to the power present in the core addressing in the form of addressing mode at the input of the multi-core fiber is greater than -5 dB. , Preferably greater than -3 dB. If only one addressing core is excited, the form of the non-addressing mode (due to the initially excited addressing mode) within a particular addressing core (s) and the addressing core (s). The ratio of the power present at the output of the multi-core to the power at the input of the multi-core in the form of the addressing mode in the initially excited addressing core is less than -10 dB, preferably less than -14 dB. High-efficiency supermode formation (defined as final crosstalk) is achieved by adjusting the effective index of refraction of each mode pair before insulation reduction (after insulation reduction as described for supermode).

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

In a preferred embodiment, an input single core optical fiber in single mode 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 index of refraction distribution and diameter of the core addressing of the multi-core fiber is selected so that all addressing modes of the multi-core fiber have different effective indices of refraction. The core to be addressed is in fu mode, and the index of refraction of that mode is chosen to suit the effective index of refraction of each of the modes in the addressing core. In regions where insulation is not reduced, supermode is formed such that the maximum crosstalk observed between any core pairs is less than -10 dB.

At certain sections, preferably 300 μm, the index of refraction is reduced and the zones separating the cores are either crushed or reduced in size (eg by tapering), resulting in reduced core insulation. , Super mode is formed and crosstalk increases. The ratio of the power present in the core addressed in the form of addressing mode at the output of the multi-core fiber to the power present in the core addressing in the form of addressing mode at the input of the multi-core fiber is greater than -5 dB. , Preferably greater than -3 dB. If only one addressing core is excited, the form of the non-addressing mode (due to the initially excited addressing mode) within a particular addressing core (s) and the addressing core (s). The ratio of the power present at the output of the multi-core to the power at the input of the multi-core in the form of the addressing mode in the initially excited addressing core is less than -10 dB, preferably less than -14 dB. The power level distribution for each addressing mode that appears at the end of the modified portion is "frozen", and this state is further transferred by the unmodified portion of the multi-core fiber.

In particular, a 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 fumode fiber, transmission is achieved by mode multiplexing. Therefore, the above-mentioned multi-core fiber in which the insulation of the core is controlled and reduced is an element (coupler) that enables an addressing mode in the fumode fiber. In this configuration, especially in the 7-core fiber, the six basic modes of the addressing core address the six higher order modes of the addressing core. The basic mode of the addressed core is excited by connecting the fiber to this core first.

Similarly, the signals within the fumode fiber can be demultiplexed using the couplers according to the invention-the information transmitted within the fumode fiber and encoded in the individual modes is individual. Can be separated into cores and even separate optical fibers.

In another preferred embodiment, an input single core optical fiber in single mode 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 index of refraction distribution and diameter of the core addressing of the multi-core fiber is selected so that all addressing modes of the multi-core fiber have different effective indices of refraction. The core to be addressed is in fu mode, and the index of refraction of that mode is chosen to suit the effective index of refraction of each of the modes in the addressing core. In regions where insulation is not reduced, supermode is formed such that the maximum crosstalk observed between any core pairs is less than -10 dB.

At certain sections, preferably 300 μm, the index of refraction is reduced and the zones separating the cores are either crushed or reduced in size (eg by tapering), resulting in reduced core insulation. , Super mode is formed and crosstalk increases. The ratio of the power present in the core addressed in the form of addressing to the output of the multi-core fiber to the power present in the core addressed in the form of addressing to the input of the multi-core fiber is greater than -5 dB. , Preferably greater than -3 dB. If only one addressing core is excited, the form of the non-addressing mode (due to the initially excited addressing mode) within a particular addressing core (s) and the addressing core (s). The ratio of the power present at the output of the multi-core to the power at the input of the multi-core in the form of the addressing mode in the initially excited addressing core is less than -10 dB, preferably less than -14 dB. The power level distribution for each addressing mode that appears at the end of the modified portion is "frozen", and this state is further transferred by the unmodified portion of the multi-core fiber.

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

Similarly, the signals within the fumode fiber can be demultiplexed using the couplers according to the invention-the information transmitted within the fumode fiber and encoded in the individual modes is individual. Can be separated into cores and even separate optical fibers.

In another preferred embodiment, the single core optical fiber is connected to a multi-core optical fiber in which the signal propagates through the addressing core, preferably a dual core addressing core. The addressed core of a multi-core fiber has high birefringence-this polarization mode has a separate effective index of refraction. The addressing core of a multi-core fiber has low birefringence-this polarization mode has the same mode effective index of refraction, hence the so-called single-mode core. One of the polarization modes in the addressing core (polarization mode x) has an effective index of refraction equal to the effective index of refraction of the mode in the addressing core of the multi-core fiber.

Preferably, at least at least 300 μm, the index of refraction is reduced and the zone separating the cores is either crushed or reduced in diameter (eg by tapering), resulting in reduced core insulation. , Super mode is formed and crosstalk increases. The ratio of the power present in the core addressed in the form of addressing to the output of the multi-core fiber to the power present in the core addressed in the form of addressing to the input of the multi-core fiber is greater than -5 dB. , Preferably greater than -3 dB. If only one addressing core is excited, the form of the non-addressing mode (due to the initially excited addressing mode) within a particular addressing core (s) and the addressing core (s). The ratio of the power present at the output of the multi-core to the power at the input of the multi-core in the form of the addressing mode in the initially excited addressing core is less than -10 dB, preferably less than -14 dB. The power level distribution for each addressing mode that appears at the end of the modified portion is "frozen", and this state is further transferred by the unmodified portion of the multi-core fiber.

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

In another preferred embodiment, the single core optical fiber is preferably connected to the addressing core of the 3-core multi-core optical fiber. The addressing core of a multi-core fiber has low birefringence-this polarization mode has the same mode effective index of refraction, hence the so-called single-mode core. High birefringence in the addressed core near the addressing core-this polarization mode has a separate effective index of refraction. One of the polarization modes in the first addressed core (polarization mode x) has an effective index of refraction equal to the mode effective index of refraction in the core to be dressed in the multi-core fiber and in the second addressed core. One of the polarization modes (polarization mode y) has an effective index of refraction equal to the mode effective index of refraction in the addressing core of the multi-core fiber.

Preferably, at least at least 300 μm, the index of refraction is reduced and the zones separating the cores are either crushed or reduced in diameter (eg by tapering), resulting in reduced core insulation. Super mode is formed and crosstalk increases. The ratio of the power present in the core addressed in the form of addressing to the output of the multi-core fiber to the power present in the core addressed in the form of addressing to the input of the multi-core fiber is greater than -5 dB. , Preferably greater than -3 dB. If only one addressing core is excited, the form of the non-addressing mode (due to the initially excited addressing mode) within a particular addressing core (s) and the addressing core (s). The ratio of the power present at the output of the multi-core to the power at the input of the multi-core in the form of the addressing mode in the initially excited addressing core is less than -10 dB, preferably less than -14 dB. The power level distribution for each addressing mode that appears at the end of the modified portion is "frozen", and this state is further transferred by the unmodified portion of the multi-core fiber.

After the perforated portion, the signal propagates through the highly birefringent core, where there is one polarization mode-the polarization mode (x) within one of the addressing cores and a second addressing core. Only the polarization mode (y) within is effectively excited. The polarization maintaining fiber is preferably connected to a birefringent core with high birefringence. This method of addressing the polarization mode allows efficient addressing of one polarization mode, thus constructing a coupler having the function of a fiber optic polarization divider.

In another preferred embodiment, the birefringent single-core optical fiber is connected to a multi-core optical fiber, preferably a dual-core addressing core. The addressing core of a multi-core fiber has high birefringence-this polarization mode has a separate effective index of refraction. The addressed core of the multi-core fiber near the addressing core also has high birefringence-this polarization mode has a separate effective index of refraction. Preferably, the addressing core and the addressing core are of the same type.

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

Preferably, at least at least 300 μm, the index of refraction is reduced and the zones separating the cores are either crushed or reduced in diameter (eg by tapering), resulting in reduced core insulation. Super mode is formed and crosstalk increases. The ratio of the power present in the core addressed in the form of addressing to the output of the multi-core fiber to the power present in the core addressing the input of the multi-core fiber in the form of addressing mode is preferably -5 dB. Greater than, and preferably less than -3 dB. The power level distribution for each addressing mode that appears at the end of the modified portion is "frozen", and this state is further transferred by the unmodified portion of the multi-core fiber.

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

In another preferred embodiment, which allows for the realization of add-drop multiplexing consisting of adding / removing one of the channels from the signal / to the signal propagating through one core, 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 preferably has at least one single mode core, and preferably at least one fumode core. The effective index of refraction of the mode in the single mode core is matched with the effective index of refraction of one mode in the fumode core. Two single-core optical fibers are mounted on both sides of the multi-core fiber, preferably the dual-core fiber, preferably with the core matched to the core of the dual-core fiber. In areas where insulation is not reduced, supermodes are formed (inefficiently formed) such that the maximum crosstalk observed between arbitrary core pairs is less than -10 dB.

At certain sections, preferably 300 μm, the index of refraction is reduced and the zones separating the cores are either crushed or reduced in diameter (eg by tapering), resulting in reduced core insulation. , Super mode is formed and crosstalk increases. The ratio of the power present in the core addressed in the form of addressing to the output of the multi-core fiber to the power present in the core addressed in the form of addressing to the input of the multi-core 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 non-addressing mode (due to the initially excited addressing mode) within a particular addressing core (s) and the initial The ratio to the power at the input of the multi-core in the form of addressing mode within the excited addressing core is less than -10 dB, preferably less than -14 dB. The power level distribution for each addressing mode that appears at the end of the modified portion is "frozen", and this state is further transferred by the unmodified portion of the multi-core fiber.

Since the mode in the single mode core and one of the modes in the fumode core have a matched index of refraction before the insulation is reduced, 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 fumode core, and the mode from the mode in the fumode core addresses the mode in the single mode core. Therefore, a type of multiplexer / demultiplexer called an add-drop multiplexer / demultiplexer can be realized. Both single-mode and fumode cores are then both an addressing core and an addressing core.

In an advantageous embodiment of the present invention, the optical fiber can be an element that deforms or changes the temperature of the optical fiber, particularly the optical fiber can be deformed to change the taper length and the tension of the tapering, and the device can be used. 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.

Although the subject matter of the present invention has been presented in detail in Examples and Drawings, these do not preclude the possibility of constructing the present invention according to the operating principles described herein.
An advantageous embodiment of the present invention, namely, a standard single-mode optical fiber (1) whose cross section (1A-1A) is shown, and a microstructured multi-core optical fiber (2) whose tapered region is shown are joined and then joined. FIG. 5 is a diagram in which an optical fiber (2) is connected to a bundle of output optical fibers arranged in a thin tube (3) whose cross section (3A-3B) is shown, and the aspect ratio is not maintained. The cross section AA is a cross section of a microstructured optical fiber that is not tapered, and the cross section BB is a tapered transition region of a microstructured multi-core optical fiber having partially collapsed (collapsed) holes. It is an enlarged view of the taper part of the microstructured multi-core optical fiber which also shows the waist region of the microstructured multi-core optical fiber which has the hole where the cross section CC is completely crushed, and the aspect ratio is not maintained. The portion (a) is a fiber area that is not tapered by the total diameter (d1), the portion (b) is a taper transition region in which the taper diameter is reduced / expanded, and the portion (c) is characterized by a diameter (d2). It is a figure which shows the tapered part of the taper of a multi-core optical fiber which is the waist part of the taper. FIG. 5 is a cross-sectional view of a standard single-mode optical fiber (1) having a core (4) of diameter (d3) and a clad (5) of diameter (d4). To construct the present invention, which has a core (4) of diameter (d5), a clad (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 crushed hole (6) with a diameter (d8), a reduced diameter core (4) with a diameter (d9), and a reduced diameter clad (5) with a diameter (d10). It is a figure which shows. It is a figure which shows the multi-core optical fiber of the microstructure which the hole is completely crushed, which is characterized by the reduced diameter core (4) of the diameter (d11), and the reduced diameter clad (5) of the diameter (d12). A core (4) of a single-mode optical fiber having a diameter of (d13), a clad (5) of a single-mode optical fiber having a diameter (d14), an inner diameter (d14) of a thin tube (capillary), and an outer diameter (d15) of the thin tube. It is a figure which shows the bundle of the standard single mode optical fiber arranged in the thin tube (7) which is shown. It is a figure which shows the advantageous embodiment of this invention which operates as NxN optical fiber couplers. The advantageous of the present invention having two inputs (outputs) and seven inputs (outputs), in which a glass rod (8), which acts as a geometric filling of the thin tube (7), is displayed on cross sections 4A-4A. It is a figure which shows the embodiment. To construct the present invention, which has a core (4) of diameter (d5), a clad (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. It is a figure which shows the advantageous embodiment of this invention which has two inputs (outputs) and one output (inputs) where (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, ie, a bundle of standard single-mode optical fibers (1) arranged in a thin tube (3) shown in cross section (3A-3A), and a tapered portion is shown. The aspect ratio is not maintained, with the microstructured multi-core fiber (2) bonded and then the fiber (2) bonded to the fumode fiber (9) shown in cross section (9A-9A). It is a figure. FIG. 5 is a cross-sectional view of a fumode optical fiber (9) of Example 6 having a core (4) having a diameter (d17) and a clad (5) having a diameter (d16). A single-mode core (4.1-4.6) with a diameter (d5.1-d5.6), a fumode core (10) with a diameter (d17) and a lattice constant (Λ), and a cladding with a diameter (d6). (5) and an exemplary multi-core fiber of Example 6 having holes (6) of diameter (d7) and not tapering or crushing, which can be used to construct the present invention. It is a figure. The cross section AA is a cross section of a microstructured optical fiber that is not tapered, and the cross section BB is a tapered transition region of a microstructured multi-core optical fiber having a partially crushed hole, and the cross section CC is complete. It is an enlarged view of the taper part of the microstructured multi-core optical fiber of Example 6 which also shows the waist region of the microstructured multi-core optical fiber which has a crushed hole, and the aspect ratio is not maintained. 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 a multiplexer and a demultiplexer correspondingly at the start end and the end of a fumode fiber (9). An advantageous embodiment of Example 7 of the present invention, namely a bundle of standard single-mode optical fibers (1) arranged in a thin tube (3), and a microstructured 4-core light (2) showing a tapered portion. ) Is joined, and then the fiber (2) is joined to the fumode fiber (9) whose cross section (9A-9A) is shown, and the aspect ratio is not maintained. A single-mode core (4.1-4.3) with a diameter (d5.1-d5.3), a fumode core (10) with a diameter (d17) and a lattice constant (Λ), and a cladding with a diameter (d6). An exemplary multi-core fiber of Example 7 that has (5) and a hole (6) of diameter (d7), is not tapered, is not crushed, and can be used to construct the present invention. It is a figure which shows. Example 8 of an advantageous embodiment of the present invention, i.e., a single-mode optical fiber (1) and a microstructured multi-core fiber with tapered portions, is joined, and then the fiber (2) maintains polarization. It is a figure which is bonded to the birefringent fiber (11), and the aspect ratio is not maintained. Single mode core (4) with diameter (d5), birefringence core (12) with minor axis (d18) and major axis (d19) with lattice constant (Λ), clad (5) with diameter (d6), and diameter. It is a figure which shows the exemplary dual core fiber of Example 8 which has a hole (6) of (d7) and is not tapered and crushed, and can be used for constructing the present invention. Example 9 of an advantageous embodiment of the present invention, i.e., a single-core optical fiber (1) and a microstructured multi-core fiber (2) with tapered portions, is joined, and then the fiber (2) maintains polarization. It is a figure which is bonded to the birefringent fiber (11), and the aspect ratio is not maintained. Single mode core (4) with diameter (d5), birefringent core (12.1 and d19.2) with minor axis (d18.1 and d18.2) and major axis (d19.1 and d19.2) with lattice constant (Λ) 12.2), a clad (5) with a diameter (d6), and a hole (6) with a diameter (d7), which is not tapered or crushed, used to construct the present invention. It is a figure which shows the exemplary dual core fiber of Example 9 possible. Example 10 of an advantageous embodiment of the present invention, i.e., a single-core optical fiber (13) and a microstructured multi-core fiber (2) whose taper is shown, is joined, and then the fiber (2) maintains polarization. It is a figure which is bonded to the birefringent fiber (11), and the aspect ratio is not maintained. Single mode core (4) with diameter (d5), birefringent core (12.1 and d19.2) with minor axis (d18.1 and d18.2) and major axis (d19.1 and d19.2) with lattice constant (Λ) 12.2), a clad (5) with a diameter (d6), and a hole (6) with a diameter (d7), which is not tapered or crushed, used to construct the present invention. It is a figure which shows the exemplary dual core fiber of Example 10 possible. Example 11 of an advantageous embodiment of the present invention, i.e., single core fibers (1) and (9), is joined to a microstructured multi-core fiber (2) with a tapered portion, followed by the fiber (2). Is joined to the output single core fibers (1) and (9), and the aspect ratio is not maintained. Single mode core (4) with diameter (d5), fumode core (10) with diameter (d17) and lattice constant (Λ), clad (5) with diameter (d6), and vacancies (6) with diameter (d7). ), And is not tapered or crushed, showing an exemplary dual core fiber of Example 11 that can be used to construct the present invention.

The coupler according to the invention includes an input optical fiber (1), which in turn is 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). It is connected to (2).

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

The single-core optical fiber (1) is preferably connected to the multi-core optical fiber (2) by fusion splicing, preferably using a fusion splicing device (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 the portion (a) until it reaches the tapered portions (b, c). In the tapered portion (b) preferably 5 mm or more, the cross section of the optical fiber: the diameters of the clad (5), the core (4) and the hole (6) are reduced (reduced).

The reduction in cross section (6) changes the propagation characteristics, the so-called core insulation reduction, resulting in the generation of supermodes in which power is transmitted from any core (s) to the remaining cores. Therefore, propagation shifts from the behavior of the isolated core to the behavior of the coupled core. Equal division of power across all cores is primarily done at the part where the hole is completely crushed (b) and at the part where the diameter of the hole is reduced / increased (c). The length of the portion (c) is 5 mm. After the portion (c) comes the taper transition zone (b). The power in each core continues to propagate independently due to the appearance (encounter) of the hole (6). In the portion (a), after passing through the tapered portion, there are seven cores (4), and a proportional amount of power propagates through these cores. With the advent of vacancies (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 the isolated core again. The multi-core optical fiber through which the seven cores propagate the signal is connected to a bundle of single single-mode optical fibers (3). The connection is made in a fusion splicing process and the manufacture of such devices and their connection to multi-core 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, which are emitted from one single-mode optical fiber (1) and to a specific recipient. Can be redirected.

The values of the tapered portions (b, c) are b = 5 mm and c = 5 mm, and the taper ratio of the multi-core fiber has the following parameters of the multi-core 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% (waist diameter of part (c) is 100 μm at maximum).

In an advantageous embodiment, the coupler according to the invention is used to split the power from two input optical fibers (1) into a bundle of seven optical fibers (3), the embodiment being a microstructured multi-core optical fiber (2). ) Is used. The single-mode optical fiber (1) is Corning's SMF-28e + fiber.

Two single-core optical fibers (1) are preferably connected to the multi-core optical fiber (2) by fusion splicing using a fusion splicer (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 portion (a) within the two cores until it reaches the taper 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 at the tapered portion (b) of 5 mm or more.

The diameter reduction in cross section (6) changes the propagation characteristics, the so-called core insulation reduction, resulting in the generation of supermode, which causes power to be transmitted from any core (s) to the remaining cores. Will be done. Therefore, propagation shifts from the behavior of the isolated core to the behavior of the coupled core. Equal division of power across all cores is primarily done at the part where the hole is completely crushed (c) and at the part where the diameter of the hole is reduced / increased (b).

The length of the portion (c) is 7 mm. After the portion (c) comes the taper transition zone (b). The power in each core continues to propagate independently with the appearance of the hole (6). In the portion (a), after passing through the tapered portion, there are seven cores (4), and a proportional amount of power propagates through these cores. With the advent of vacancies (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 the isolated core again. The multi-core optical fiber through which the seven cores propagate the signal is connected to a bundle of single single-mode optical fibers (3). The connection is made in a fusion splicing process and the manufacture of such devices and their connection to multi-core 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, which are emitted from the two single-mode optical fibers (1) and to a specific recipient. Can be redirected.

The values of the tapered portions (b, c) are b = 5 mm and c = 5 mm, and the taper ratio of the multi-core fiber has the following parameters of the multi-core 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% (waist diameter of part (c) is 100 μm at maximum).

In an advantageous embodiment of the invention shown in FIG. 9, where the present invention is used to couple from each of the seven input optical fibers (1) to seven output optical fibers (3) in a bundle, of microstructure. 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 is sent to a microstructured multi-core optical fiber (2).

The single-mode optical fiber (1) is preferably connected to the multi-core optical fiber (2) by fusion splicing using a fusion splicer (Vytren GPX-3400 or Fujikura FSM 70). After being sent to the multi-core optical fiber (2), the signal propagates through the portion (a) of the multi-core fiber that is still in the seven cores until it reaches the taper 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 at the tapered portion (b) of 5 mm or more. Due to the diameter reduction of the cross section (6), the propagation characteristics, so-called core insulation reduction, are changed, and as a result, a super mode is generated so that the signal can be transmitted between the cores. Therefore, propagation shifts from the behavior of the isolated core to the behavior of the coupled core. The mixing of the signals between the cores is mainly performed in the portion (c) where the hole is completely crushed and the portion (b) where the diameter of the hole is reduced / increased. The length of the portion (c) is 7 mm. After the portion (c) comes the taper transition zone (b). The power in each core continues to propagate independently with the appearance of the hole (6). In the portion (a), after passing through the tapered portion, there are seven cores (4), and a proportional amount of power propagates through these cores. With the advent of vacancies (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 the isolated core again. The multi-core optical fiber through which the seven cores propagate the signal is connected to a bundle of single single-mode optical fibers (3). The connection is made in a fusion splicing process and the manufacture of such devices and their connection to multi-core optical fibers are described in detail in the appropriate literature. After passing through a bundle of single-mode fiber optics (3), seven signals of independent single-mode fiber optics are obtained, which contain information from all seven input fiber optics and are specific recipients. Can be redirected to.

The values of the tapered portions (b, c) are b = 5 mm and c = 7 mm, and the taper ratio of the multi-core fiber has the following parameters of the multi-core 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% (waist diameter of part (c) is 100 μm at maximum).

In another embodiment of the invention shown in FIG. 12, where the present 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, it 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 the microstructured multi-core optical fiber (2).

The single-mode optical fiber (1) is connected to the multi-core optical fiber (2) by fusion splicing using a fusion splicer (Vytren GPX-3400 or Fujikura FSM 70). After being sent to the multi-core optical fiber (2), the signal further propagates in the core within the portion (a) to which the multi-core fiber is connected until it reaches 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 at the tapered portion (b) of 6 mm or more. Due to the diameter reduction of the cross section (6), the propagation characteristics, so-called core insulation reduction, are changed, 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. Therefore, propagation shifts from the behavior of the isolated core to the behavior of the coupled core. Depending on the length of the taper, the signal can be separated between the cores at any ratio. When the tapered portion (tapered waist region) is 10 mm, the signal propagates only in the core to which the single core fiber is connected. In the case of a tapered portion (tapered waist region) extended by 8 mε, the signal is sent to the core in the vicinity completely. The intermediate value corresponds to the situation where the power propagates through both cores in various relations. The piezoelectricity around which the multi-core optical fiber (2) is wound or attached allows the taper length to be varied, resulting in signal switching between specific cores while the device operates with the same optical switch function.

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

In an advantageous embodiment of the invention shown in FIG. 12, where the present invention is used to separate two input wavelengths into specific output optical fibers, a microstructured multi-core optical fiber (2) is utilized. In this embodiment, it 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 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. The single-mode optical fiber (1) is connected to the multi-core optical fiber (2) by fusion splicing using a fusion splicer (Vytren GPX-3400 or Fujikura FSM 70). After being sent to the multi-core optical fiber (2), the signal further propagates in the core within the portion (a) to which the multi-core fiber is connected until it reaches 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 at the tapered portion (b) of 3 mm or more. Depending on the diameter of the cross section (6), the propagation characteristics, so-called core insulation reduction, are changed, and as a result, a super mode is generated, so that a signal can be transmitted from the first signal carrier core to the second core. become. Therefore, propagation shifts from the behavior of the isolated core to the behavior of the coupled core. Depending on the taper length, the signal can be separated between the cores at any ratio. When the tapered portion (tapered waist region) is 6 mm, the wavelength of 1550 nm propagates only in the core to which the single core fiber is connected. Also, the wavelength of 1310 nm propagates only in the nearby cores. When the tapered portion (tapered waist region) is extended by 8 mε, the other wavelengths of 1550 nm and 980 nm are efficiently separated between the cores in this embodiment. Since the fiber can be extended, the taper length can be changed, and various wavelength separation configurations are possible. In addition, the wavelengths described herein have a taper length that allows the two wavelengths to be separated into specific communication channels. Such a field of use of the present invention is the implementation of the concept of WDM (Wavelength Division Multiplexing) couplers.

The values of the tapered portions (b, c) are b = 3 mm and c = 6 mm, and the taper ratio of the multi-core fiber has 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, which is 30%.

By the coupler according to the present invention, a core insulated in the reduced area of refractive index 6 in the form of an air-filled hole and a single-mode core with a wavelength of 1550 nm (4.1, 4.2, 4.3, 4.4). Allows the construction of elements for controlled mode addressing, including a multi-core (7-core) optical fiber (2) with, 4.5, 4.6), the core having a gradual index of refraction. It has a basic mode in which the distribution and the effective refractive index are different. For the 7-core fiber (2) having an insulating core, a fan-in / fan-out type element is used, and a 7-input single core fiber (2) is arranged in a thin tube (3), which is the opposite of the multi-core fiber. A single-core fumode output fiber (9) is attached to the side, and in the portion of the multi-core optical fiber (2), insulation is reduced by crushing the structure of the insulating hole 6. Geometric midpoints of microstructural elements (holes and cores) are placed on the hexagonal lattice, the lattice constant (Λ) is 20 μm, the diameter of the insulating holes is 10 μm, and the core (10) -dressing. The core multi-core to be made has a gradual index of refraction distribution, which is in fu mode and has a separate effective index of refraction in a particular mode. In the vicinity of the core (10) to be addressed, there is an addressing core (4.1 to 4.6) having a stepwise index of refraction distribution, and the effective index of refraction of the mode is each of the cores (10) to be addressed. Is selected to match the effective index of refraction of the mode.

In areas where insulation is not reduced, a supermode 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) has been modified so that the structure of the holes (6) is crushed in some parts, even though this part efficiently forms a supermode on the addressing core and the addressing core. There is enough length. The length of the crushed portion of the hole (6) is 5 mm, and the taper ratio is 0.5%.

At (c) = 5 mm, reduced (reduced) core insulation is formed as a result of the holes separating the cores being crushed, supermode is formed and crosstalk is increased-addressing at the output of the multi-core fiber. The ratio of the power present in the addressing core in the form of the mode to be addressed to the power present in the addressing core in the form of the addressing mode at the input of the multi-core fiber is greater than -3 dB. When only one addressing core is excited, the form of the non-addressing mode (due to the initially excited addressing mode) within a particular addressing core (s) and the addressing core (s). The ratio of the power present at the output of the multi-core to the power in the addressing mode form of the initially excited addressing core at the input of the multi-core is less than -14 dB. The power level distribution for each addressing mode that appears at the end of the modified portion is "frozen", and this state is further transferred by the unmodified portion of the multi-core 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 coupler configuration in the above-mentioned multi-core fiber in which the insulation of the core is controlled and reduced (reduced) is an element (coupler) that enables the addressing mode in the fumode fiber.

Similarly, the signals within the fumode fiber can be demultiplexed using the couplers according to the invention-the information transmitted within the fumode fiber and encoded in a particular mode is individual. Can be separated into cores and even separate optical fibers. A transmission system using mode multiplexing can be constructed by using a coupler in the configuration of a multiplexer and demultiplexer having a connection to a fumode optical fiber (FIG. 17).

Dimensions of fumode fiber (9): clad diameter d16 = 125 μm; fumode core (10) −diameter d17 = 20 μm, 5.8 mol% GeO ₂ doped SiO ₂
Dimensions of multi-core 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 = 12.6 μm, 5.8 mol% GeO ₂ doped SiO ₂ ;
-Core (4.2) -diameter d5.2 = 8 μm, 5.8 mol% GeO ₂ doped SiO ₂ ;
-Core (4.3) -Diameter d5.3 = 6.4 μm, 5.8 mol% GeO ₂ doped SiO ₂ ;
-Core (4.4) -Diameter d5.4 = 5.4 μm, 5.8 mol% Geo ₂ doped SiO ₂ ;
-Core (4.5) -Diameter d5.5 = 4.4 μm, 5.8 mol% GeO ₂ doped SiO ₂ ;
-Core (4.6) -Diameter d5.6 = 2 μm, 5.8 mol% GeO ₂ doped SiO ₂ ;
- cladding (5) - diameter d6 = 250 [mu] m, _SiO doped with 0 mol% of GeO ₂ 2;
− Lattice constant (Λ) = 20 μm
Dimensions of hole (6): diameter d7 = 10 μm
Tapered 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 Example 6 is shown in FIGS. 3, 13, 14, 15, 15, 16 and 17. In this configuration, the six basic modes of the addressing core address the six higher-order modes of the addressing core. The basic mode of the addressed core is excited by first connecting the fiber to this core.

By the coupler according to the present invention, a core insulated in the reduced area of the refractive index (6) in the form of an air-filled hole and a single-mode core (4.1, 4.2, 4.3) having a wavelength of 1550 nm. It is possible to construct elements for a controlled dressing mode having a multi-core optical fiber (2) having a gradual index of refraction and a basic mode in which the effective index of refraction is different. A 3-input single-core fiber (2) is arranged in a thin tube (3) in a multi-core-4-core fiber (2) using a fan-in / fan-out type element, and a single core is arranged on the opposite side of the multi-core fiber. The fumode output fiber (9) of the above is 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). Geometric midpoints of microstructural elements (holes and cores) are placed on the hexagonal lattice, the lattice constant (Λ) is 20 μm, the diameter of the insulating holes is 10 μm, and the core (10) -dressing. The multi-core of the core to be made has a gradual index of refraction distribution, which is in fu mode and has a separate effective index of refraction in a particular mode. In the vicinity of the core (10) to be addressed, there is an addressing core (4.1 to 4.3) having a stepwise refractive index distribution, and the effective refractive index of the mode is each of the cores (10) to be addressed. Is selected to match the effective index of refraction of the mode. In areas where insulation is not reduced, supermodes are 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) has been modified so that the structure of the holes (6) is crushed in some parts, even though this part efficiently forms a supermode on the addressing core and the addressing core. There is enough length. The length of the crushed portion of the hole (6) is 5 mm, the taper transition region (b) = 2 mm, and the taper ratio is 10%.

At (c) = 5 mm, reduced (reduced) core insulation is formed as a result of the holes separating the cores being crushed, supermode is formed and crosstalk is increased-addressing at the output of the multi-core fiber. The ratio of the power present in the addressing core in the form of mode to be addressed to the power present in the addressing core in the form of addressing at the input of the multi-core fiber is greater than -3 dB. When only one addressing core is excited, the form of the non-addressing mode (due to the initially excited addressing mode) within a particular addressing core (s) and the addressing core (s). The ratio of the power present at the output of the multi-core to the power in the form of addressing mode within the initially excited addressing core (s) at the input of the multi-core is less than -14 dB. The power level distribution for each addressing mode that appears at the end of the modified portion is "frozen", and this state is further transferred by the unmodified portion of the multi-core fiber.

The output end single-core fumode fiber (9) of the multi-core fiber (2) is connected with 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 three modes. Therefore, the coupler configuration of the multi-core fiber in which the insulation of the core is controlled and reduced (reduced) is an element (coupler) that enables the addressing mode in the fumode fiber.

Similarly, the signals within the fumode fiber can be demultiplexed using the couplers according to the invention-the information transmitted within the fumode fiber and encoded in a particular mode is individual. Can be separated into cores and even separate optical fibers. A transmission system using mode multiplexing can be constructed by using a coupler in the configuration of a multiplexer and demultiplexer having a connection to a fumode optical fiber.

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 multi-core 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 = 10 μm, 2 mol% GeO ₂ doped SiO ₂ ;
-Core (4.2) -Diameter d5.2 = 8 μm, 11.3 mol% GeO ₂ doped SiO ₂ ;
-Core (4.3) -diameter d5.3 = 10 μm, 6.1 mol% GeO ₂ doped SiO ₂ ;
- cladding (5) - diameter d6 = 250 [mu] m, _SiO doped with 0 mol% of GeO ₂ 2;
− Lattice constant (Λ) = 16 μm
Dimensions of hole (6): diameter d7 = 8 μm
Tapered 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 FIGS. 3, 18, and 19. In this configuration, the three basic modes of the addressing core address the two higher-order modes of the addressing core.

Controlled by a coupler according to the invention, the core comprises a multi-core optical fiber (2) in which the core has an effective index of refraction in 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 dressing in a change mode. In the vicinity of the addressing core is a single-mode core with a wavelength of 1550 nm having a gradual index of refraction selected to match one effective index of refraction of the polarization mode (polarization mode x) within the addressing core (12). There is (4). The input single core fiber (1) is attached to the multi-core fiber (2) having an insulated core, and the single core double refraction polarization maintaining fiber (11) is attached to the opposite side of the multi-core fiber, and the multi-core optical 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 multi-core fiber (2) has a gradual index of refraction, is birefringent, and has a distinct effective index of refraction for a particular polarization mode. In areas where insulation is not reduced, a supermode 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 the structure of the hole (6) is crushed at some part. The length of the crushed portion of the hole (6) is (c) = 3 mm, the taper transition region (b) = 2 mm, and the taper ratio is 20%.

At the portion (c) = 5 mm, reduced (reduced) core insulation is formed as a result of the holes separating the cores being crushed, and crosstalk is increased. The reduced insulation results in the formation of supermodes, resulting in increased crosstalk-at the power present in the addressed core in the form of addressing 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 addressing mode is greater than -4 dB. Further, the ratio of the power present at the output of the multi-core in the non-addressing mode form within the addressed core to the power in the initial addressing mode form at the input of the multi-core is less than -12 dB. The power level distribution for each addressing mode that appears at the end of the modified portion is "frozen", and this state is further transferred by the unmodified portion of the multi-core fiber.

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

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

Dimensions of multi-core 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 μm, major axis d19 = 12.4 μm, 3.5 mol% GeO ₂ doped SiO ₂ ;
_{-Clad (5) -SiO 2} (quartz glass) doped with _{0 mol% GeO 2} with a diameter of d6 = 125 μm.
− Lattice constant (Λ) = 16 μm
Dimensions of hole (6): diameter d7 = 10m
Tapered parameters:
-Part (b) = 2 mm
-Part (c) = 3 mm
-Diameter d1 = 125 μm
-Taper ratio = 20% (d2 = 100 μm)

The invention of Example 8 is shown in FIGS. 3, 20, and 21. In this configuration, the basic mode of the addressing core (4) addresses the polarization mode of the core (12) to be addressed.

According to the coupler according to the present invention, the multi-core-core has an effective refractive index with different modes, and two of the cores of the multi-core fiber (2) -core (12.1) and core (12.2) are birefringent. It is possible to construct an element for controlled addressing with the characteristic 3-core fiber 2. In the vicinity of the core to be addressed, a stepwise index selected so that the effective index of refraction matches the effective index of refraction of the polarization mode in the cores (12.1) and (12.2) to be addressed is provided. There is a single mode core (4) having a wavelength of 1550 nm. The input single core fiber (1) is attached to the multi-core fiber (2) having an insulated core, and the single core double refraction polarization maintaining fiber (11) is attached to the opposite side of the multi-core fiber, and the multi-core optical 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 multi-core fiber (2) have a gradual index of refraction, are birefringent, and have a separate effective index of refraction for a particular polarization mode. ing. In areas where insulation is not reduced, a supermode 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 the structure of the hole (6) is crushed at some part. The length of the crushed portion of the hole (6) is (c) = 5 mm, the taper transition region (b) = 2 mm, and the taper ratio is 10%.

At the portion (c) = 5 mm, reduced (reduced) core insulation is formed as a result of the holes separating the cores being crushed, and crosstalk is increased. The reduced insulation results in the formation of supermodes, resulting in increased crosstalk-at the power present in the addressed core in the form of addressing 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 addressing mode is greater than -4 dB. Moreover, the ratio of the power present at the output of the multi-core form in the non-addressing mode form within a particular addressed core to the power in the initial addressing mode form at the input of the multi-core is less than -12 dB. The power level distribution for each addressing mode that appears at the end of the modified portion is "frozen", and this state is further transferred by the unmodified portion of the multi-core fiber.

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

Therefore, the coupler structure in a multi-core fiber in which the reduction (reduction) of core insulation is controlled is an element (coupler) that allows addressing of the polarization mode and is therefore an optical fiber polarizer that divides the polarization state when constructed. .. In the reverse configuration, the coupler can be used as a polarizing combiner.

Dimensions of multi-core 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 = 6 μm, major axis d19.1 = 12.2 μm, 3.5 mol% GeO ₂ doped SiO ₂ ;
-Core (12.2) -minor axis d18.2 = 6 μm, major axis d19.2 = 12.2 μm, 3.5 mol% GeO ₂ doped SiO ₂ ;
_{-Clad (5) -SiO 2} (quartz glass) doped with _{0 mol% GeO 2} with a diameter of d6 = 125 μm.
− Lattice constant (Λ) = 16 μm
Dimensions of hole (6): diameter d7 = 10m
Tapered parameters:
-Part (b) = 5 mm
-Part (c) = 5 mm
-Diameter d1 = 125 μm
-Taper ratio = 10% (d2 = 112.5 μm)

The invention of Example 9 is shown in FIGS. 3, 22, and 23. In this configuration, the three basic modes of the core (4) to be addressed address the polarization modes of the cores 12.1 and 12.2 to be addressed.

The coupler according to the invention allows the construction of an element for addressing a controlled polarization mode with a multi-core-birefringent core (12.1) and a dual-core optical fiber (2) with a core (12.2). It will be possible. The core is homogenius. A single-core birefringence polarization maintenance fiber (13) is attached to the multi-core fiber (2) having an insulated core, and a single-core birefringence polarization maintenance fiber (11) is attached to the opposite side of the multi-core 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 multi-core fiber (2)-cores (12.1) and (12.2) have different gradual indices of refraction and are birefringent. In the vicinity of the core to be addressed, a stepwise index selected so that the effective index of refraction matches the effective index of refraction of the polarization mode in the cores (12.1) and (12.2) to be addressed is provided. There is a single mode core (4) having a wavelength of 1550 nm. An input single-core birefringence polarization maintenance fiber (13) is attached to the multi-core fiber (2) having an insulated core, and an output single-core birefringence polarization maintenance fiber (11) is attached to the opposite side of the multi-core 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 gradual index of refraction and a separate effective index of refraction for a particular polarization mode. In areas where insulation is not reduced, a supermode 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 the structure of the hole (6) is crushed at some part. The length of the crushed portion of the hole (6) is (c) = 5 mm, the taper transition region (b) = 2 mm, and the taper ratio is 10%.

At the portion (c) = 5 mm, reduced (reduced) core insulation is formed as a result of the holes separating the cores being crushed, and crosstalk is increased. The reduced insulation results in the formation of supermodes, resulting in increased crosstalk-the power present in the addressing core in the form of addressing mode on the output multicore fiber and at the input of the multicore fiber. The ratio to the power present in the addressing core in the form of addressing mode is greater than -3 dB.

After the perforated portion, 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 polarization with birefringence is connected to a core with high birefringence.

Therefore, the coupler structure in a multi-core fiber in which the reduction (reduction) of core insulation is controlled is an element (coupler) that allows addressing of the polarization mode, and thus when constructing a fiber optical coupler (splitter) polarization maintenance. In addition, the signal existing at the starting end of the core (12.1) is divided into cores (12.1) and (12.2), and the polarized state is maintained. In the reverse configuration, the coupler can be used as a polarizing combiner.

Dimensions of multi-core fiber (2):
-Core (12.1) -minor axis d18.1 = 6 μm, major axis d19.1 = 12.4 μm, 3.5 mol% GeO ₂ doped SiO ₂ ;
-Core (12.2) -Short axis d18.2 = 6 μm, major axis d19.2 = 12.4 μm, 3.5 mol% GeO ₂ doped SiO ₂ ;
_{-Clad (5) -SiO 2} (quartz glass) doped with _{0 mol% GeO 2} with a diameter of d6 = 125 μm.
− Lattice constant (Λ) = 16 μm
Dimensions of hole (6): diameter d7 = 10m
Tapered parameters:
-Part (b) = 5 mm
-Part (c) = 5 mm
-Diameter d1 = 125 μm
-Taper ratio = 10% (d2 = 112.5 μm)

The invention of Example 10 is shown in FIGS. 3, 24 and 25. In this configuration, the addressing core 12.1 addresses the polarization mode of the core 12.2 to which it is addressed.

The coupler according to the invention allows the construction of elements for controlled dressing, including a multi-core optical fiber (2) with a core insulated in a reduced area of refractive index (6) in the form of an air-filled hole. become. One of the cores (4.3) is a single-mode core with a wavelength of 1550 nm and has a gradual index of refraction distribution, and the second core (10) is a fumode core, which is also a gradual refraction. It has a rate distribution. Multi-core-A dual-core fiber (2) with an isolated core is fitted with two input single-core fibers (1) and (9) and two output single-core fibers (1) on the opposite side of the multi-core optical fiber. ) 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 (holes and cores) is equal to the lattice constant (Λ), the diameter of the insulating holes is 10 μm, the core (10) -the multi-core to which the core is addressed has a gradual index of refraction distribution. It is a fu mode and has a separate effective index of refraction for a particular mode. In the vicinity of the core (10) to be addressed, there is an addressing core (4.3) having a stepwise index of refraction, and the effective index of refraction of that mode is the mode (th. It is selected to match one effective index of refraction (3rd order mode). Since the effective index of refraction is matched between the mode of the core (4.3) and one of the modes of the core (10), a super mode is formed before the reduction of the insulation and therefore in the part where the insulation is reduced. NS. 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 both addressing cores and at the same time addressing cores.

In areas where insulation is not reduced, a supermode 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 a structure of holes (6) long enough to form a supermode on the cores to be addressed and the cores (10) and (4.3) to be addressed in some parts. Is modified to be crushed. The length of the crushed 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 (c) = 5 mm, 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 supermode formation and crosstalk. -The ratio of the power present in the addressing core in the form of addressing mode on the output multi-core fiber to the power present in the addressing core in the form of addressing mode at the input of the multi-core fiber- Greater than 3 dB. If only one addressing core is excited, the form of the non-addressing mode (due to the initially excited addressing mode) within a particular addressing core (s) and the addressing core (s). The ratio of the power present at the output of the multi-core to the power in the form of the addressing mode within the initially excited addressing core at the input of the multi-core is less than -14 dB. The power level distribution for each addressing mode that appears at the end of the modified portion is "frozen", and this state is further transferred by the unmodified portion of the multi-core fiber.

Dimensions of fumode fiber (9): cladding diameter d16 = 125 μm, core diameter d17 = 20 μm, 5.8 mol% GeO ₂ doped SiO ₂ ;
Dimensions of multi-core fiber 2:
- 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 = 6.4 μm, 5.8 mol% GeO ₂ doped SiO ₂ ;
_{-Clad (5) -SiO 2} (quartz glass) doped with _{0 mol% GeO 2} with a diameter of d6 = 250 μm.
− Lattice constant (Λ) = 20 μm
Dimensions of hole (6): diameter d7 = 10 μm
Tapered parameters:
-Part (b) = 2 mm
-Part (c) = 5 mm
-Diameter d1 = 250 μm
-Taper ratio = 10% (d2 = 225 μm)

The invention of this example is shown in FIGS. 3, 26 and 27. In this configuration (multiplexer), the mode of core 4.3 addresses the third higher mode of the core, and the third higher mode from core 10 addresses the mode of core 4.3. Further, another mode propagates to the fumode core due to the initial excitation. In this configuration, it is imperative to add additional signals to the core 10 propagating in another mode, and one signal can be dropped from another signal propagating in this core. An embodiment relates to the realization of add-drop multiplexing by adding / removing one of the channels to / from a signal propagating through one core.

The following are the inventions described at the time of filing.
<Claim 1>
A fiber optical coupler comprising a multi-core optical fiber with an insulated core, the core insulation being configured as an expression of a zone characterized by a reduced refraction near the core, with N output optical fibers. A core by including at least one input optical fiber bonded to a multi-core optical fiber of at least N-core with a bonded, insulated core and by reducing the size of the zone of reduced refraction near the core. A fiber optical coupler characterized in that the insulation of the light is reduced in at least one portion of a multi-core optical fiber.
<Claim 2>
The fiber optical coupler according to claim 1, wherein the component multi-core optical fiber has a core having air-assisted insulation.
<Claim 3>
The fiber optical coupler according to claim 1 or 2, wherein at least one fragment of the multi-core optical fiber is tapered at a portion and the holes thereof are crushed.
<Claim 4>
The fiber optical coupler according to claim 1, 2 or 3, wherein at least one fragment of the multi-core optical fiber and its holes are crushed without being tapered.
<Claim 5>
The fiber optical coupler according to claim 1 or 2, 3 or 4, wherein an optical fiber whose core insulation guarantees the occurrence of crosstalk at a level of 10 dB or less is used.
<Claim 6>
The fiber optical 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>
Claim 1 or 2 or 3 or 4 or 5 characterized in that the length of the taper portion is greater than 300 μm and the designed signal division level depends on the length and degree of tapering and / or the degree of hole fracture. Or the fiber optical coupler according to 6.
<Claim 8>
The fiber optical 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>
The fiber according to claim 1 or 2 or 3 or 4 or 5 or 6 or 7 or 8, wherein the taper ratio is 0 to 95%, and the taper ratio is considered to be a reduction rate of the fiber cross section. Optical coupler.
<Claim 10>
The fiber optical coupler according to claim 1 or 2 or 3 or 4 or 5 or 6 or 7 or 8 or 9, wherein the single optical fiber connected to the multi-core optical fiber is a standard single-mode optical fiber. ..
<Claim 11>
Claimed that a single optical fiber connected to a multicore optical fiber is a standard single mode optical fiber in which those cores are etched and / or tapered so as to be aligned with the core of the multicore optical fiber. Item 2. 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>
The fiber optical according to claim 1 or 2 or 3 or 4 or 5 or 6 or 7 or 8 or 9 or 10 or 11, wherein the single optical fiber connected to the multi-core optical fiber is arranged in a thin tube. Coupler.
<Claim 13>
The single optical fiber connected to a multi-core optical fiber is according to claim 1 or 2 or 3 or 4 or 5 or 6 or 7 or 8 or 9 or 10 or 11 or 12, wherein the single optical fiber is connected by a fusion splicer. Fiber optic coupler.
<Claim 14>
At least one core of the multi-core fiber is the core to be attached, so that it is multi-mode (fu-mode) and / or birefringent at the wavelength used, and at least one core is the core to be attached. Yes, at least one at least one single-core input fiber is connected to the multi-core fiber, at least one at least one at least single-core output fiber is attached to the opposite side of the multi-core fiber, and the insulation of the core is reduced in at least one part of the multi-core fiber. The fiber optical coupler according to any one of claims 1 to 13, wherein the power existing in the core addressed at the output of the multi-core fiber is larger than the power at the input of the multi-core fiber.
<Claim 15>
The fiber optical coupler according to claim 14, wherein the insulating structure has the form of a zone with reduced refractive index selected from pores filled with air or gas, or solid or liquid.
<Claim 16>
The fiber optical coupler according to claim 14 or 15, wherein the addressing core is in a single mode at the wavelength used.
<Claim 17>
The fiber optical coupler according to claim 14 or 16, wherein the addressing one or more cores are birefringent at the wavelength used and / or multimode (fumode).
<Claim 18>
The fiber optical coupler according to claim 14, 15 or 16 or 17, wherein the addressing core has different modes of refractive index.
<Claim 19>
The fiber optical coupler according to claim 14 or 15 or 16 or 17 or 18, wherein the addressing core and addressing cord have the same index of refraction in a particular mode.
<Claim 20>
The ratio of the power present in the addressing core in the form of addressing mode at the output of the multi-core fiber to the power present in the addressing core in the form of addressing mode at the input of the multi-core fiber is -5 dB. The fiber optical coupler according to claim 14 or 15 or 16 or 17 or 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 a non-addressing mode (due to the initially excited addressing mode) of one or more cores to be addressed and the core to be addressed. 14 or 15 or 16 or 17 or 18 or 19 of claim 14 or 15 or 16 or 17 or 18 or 19 characterized in that the ratio of to the power at the input of the multi-core in the form of addressing mode within the initially excited addressing core is less than -10 dB. Or the fiber optical coupler according to 20.
<Claim 22>
14. Or the fiber optical coupler according to 21.
<Claim 23>
The fiber optical coupler according to any one of claims 1 to 22, wherein the zone in which the refractive index is reduced is filled with a fiber clad, and the entire fiber clad serves as a refractive index reduction zone.
<Claim 24>
13. Fiber optical coupler.
<Claim 25>
The fiber optical coupler according to any one of claims 1 to 24, wherein 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 reverse configuration (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 cores to be addressed. ), The fiber optical coupler according to any one of claims 1 to 25.
<Claim 27>
Coupling between cores, and thus division of signals (its power and / or wavelength), taper length (elongation) and / or tension, especially using mechanical devices that wind the fiber around a piezoelectric structure or deform the fiber. The fiber optical coupler according to any one of claims 1 to 26, which can be changed by changing (compression, bending, twisting) and / or temperature.

Claims (14)

Multi-core optical fiber with an insulated core and
Single-core input optical fibers (1a, 9a, 9, 13) connected to the core of the multi-core optical fiber having the insulated core, and
A fiber optical coupler comprising a single-core output optical fiber (1b, 9b, 9, 11) connected to the core of a multi-core optical fiber having an insulated core at the other end.
The multi-core optical fiber having an insulated core is a microstructured multi-core optical fiber (2) having a plurality of cores insulated by axial holes (6) arranged between them.
The same number of holes (6) are arranged in the same arrangement between any two adjacent cores of a multi-core optical fiber having the insulated core.
The microstructured multi-core optical fiber (2) has a portion modified so that at least a part of the hole (6) is crushed by tapering to reduce the insulation of the core, and the modified portion. Is longer than 300 μm,
The multi-core optical fiber (2) has a core (4) insulated in the form of a hole (6) filled with air or gas or solid or liquid.
A fiber optical coupler characterized in that an optical fiber is used that guarantees the occurrence of crosstalk at a level of less than -10 dB in the insulating portion of the core (4) before and after the portion where the insulation of the core is reduced. Taper ratio in said modified portion of the multi-core optical fiber microstructure (2) is characterized in that area by der from 0 to 95% of the tapering front of the cross-sectional size of the multi-core optical fiber (2) The fiber optical coupler according to claim 1. The single-core input optical fiber (1a) and the single-core output optical fiber (1b) are standard single-mode optical fibers, and are etched to align these cores with the cores of the multi-core optical fiber (2). The fiber optic coupler according to claim 1 or 2 , characterized in that it is tapered and / or tapered. The fiber optical coupler according to any one of claims 1 to 3 , wherein the single-core input optical fiber (1a) is arranged in a thin tube. The fiber optical coupler according to any one of claims 1 to 3 , wherein the single-core output optical fiber (1b) is arranged in a thin tube. Claims that at least one of the cores of a microstructured multi-core optical fiber (2) is standard and / or birefringent at the wavelength used and is a single-mode, multi-mode or fu-mode fiber. Item 5. The fiber optical coupler according to any one of Items 1 to 5. The fiber optical coupler according to claim 6 , wherein the effective refractive index of the core mode of the microstructured multi-core optical fiber (2) and the single-core input optical fiber (1a) are different. Claim 6 or 7, characterized in that it has a multi-core optical fiber (2) and the core is the same refractive index of a particular mode of single-core input optical fiber (1a) and a single-core output optical fiber (1b) of the microstructure The fiber optic coupler according to. The power present in the single-core input optical fiber (1a) according to any one of claims 6-8 in which the ratio of the power present in the single-core output optical fiber (1b) being greater than -5dB against Fiber optical coupler. When exciting the only one core of the multi-core optical fiber (2), the ratio of power present in the single-core output optical fiber (1b) against the power present in the single-core input optical fiber (1a) is initially excited The fiber optic coupler according to any one of claims 6 to 9 , wherein the core is greater than -10 dB. The fiber optical coupler according to any one of claims 1 to 10 , wherein the hole (6) is filled with the fiber clad (5) material, and the entire fiber clad serves as a zone having a reduced refractive index. .. One or more fibers (1a, 1b) or (9, 9a, 9b) or (11) or (13) connected to the multi-core fiber (2) are single mode (1a, 1b) and / or multiple. The fiber optical coupler according to any one of claims 1 to 11 , characterized in that it is selected from refractive (13) and / or multi-mode or fu-mode fibers. One or more fibers (1a, 1b) or (9, 9a, 9b) or (11) or (13) connected to the multi-core fiber (2) correspond to the core refractive index distribution of the multi-core fiber. The fiber optical coupler according to any one of claims 1 to 11 , wherein the fiber optical coupler has a refractive index distribution of the core. The mode is demultiplexed, the role of the single core input optical fiber (1a, 9b, 13) is played by the single core output optical fiber (1b, 9b, 11), and the role of the single core output optical fiber (1b, 9b, 11). The fiber optical coupler according to any one of claims 1 to 13 , characterized in that the above is achieved by a single core input optical fiber (1a, 9b, 13).

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