Connection loss estimation device and estimation method

Abstract

The objective is to provide an apparatus and method that can estimate the connection loss for each propagation mode, even when multimode optical fibers with different mode field diameters are connected. [Solution] The connection loss estimation device according to the present invention obtains the input and output mode field diameters (W ff1 ,W ff2 Using the axial misalignment (s) at the connection point and the coupling efficiency approximation formula (equation C1 or C2) derived from the overlap integral of higher-order Gaussian functions, the propagation mode (LP) of the desired order (ν,μ) is determined. νμ We decided to calculate the connection loss of the )

Description

[Technical Field]

[0001] This disclosure relates to an apparatus and method for estimating the connection loss of a multimode optical fiber. [Background technology]

[0002] Multimode optical fibers and multimode multicore optical fibers are promising optical fibers for realizing future high-capacity optical fiber communications. Optical fiber connections are essential in the construction of optical fiber communication systems. Connection loss in optical fibers is closely related to the electric field distribution of the modes propagating through the fiber. Since multiple modes can propagate in multimode optical fibers, it is important to understand the connection loss of each propagating mode.

[0003] Non-patent document 1 discloses a method for estimating the connection loss between propagation modes in a multi-mode optical fiber using the mode field diameter of any propagation mode. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] A. Nakamura et al., “Definition of mode field diameter for few-mode fibers based on stationary expression of propagation constant,” in Proc. Opt. Fiber Commun. Conf., 2023, Art. no. M4B.2. [Overview of the project] [Problems that the invention aims to solve]

[0005] The method disclosed in Non-Patent Document 1 assumes that the mode field diameters of the propagation modes of the connected multi-mode optical fibers are equal. In other words, the method disclosed in Non-Patent Document 1 has the problem of being unable to correctly estimate the connection loss for each propagation mode when connecting multi-mode optical fibers with different mode field diameters.

[0006] To solve the aforementioned problems, the present invention aims to provide an apparatus and method that can estimate the connection loss for each propagation mode even when multimode optical fibers with different mode field diameters are connected. [Means for solving the problem]

[0007] To achieve the above objective, the connection loss estimation device according to the present invention uses the acquired input and output mode field diameters (W ff1 ,W ff2 Using the axial misalignment (s) at the connection point and the coupling efficiency approximation formula (equation C1 or C2) derived from the overlap integral of higher-order Gaussian functions, the propagation mode (LP) of the desired order (ν,μ) is determined. νμ We decided to calculate the connection loss of the )

[0008] Specifically, the connection loss estimation device according to the present invention is a device for estimating the state of the connection point of two multimode optical fibers connected in series, An arithmetic unit having a number C1 or a number C2 into which a condition value is substituted, An input device for inputting the aforementioned conditional value to the calculation device, An output device that outputs the calculation results calculated by the aforementioned computing device, It is equipped with, The aforementioned computing device is The above condition value corresponds to the mode field diameter (W) of each of the two multimode optical fibers. ff1 ,W ff2 ) when Substitute the above condition value into number C1 or number C2, and determine the propagation mode (LP νμ ) For each connection point, the relationship between the amount of axial misalignment (s) and the connection loss is calculated, and this relationship is used as the calculation result. is characterized by. [Number] [Number] However, η νμ is the coupling efficiency between the LP νμ modes at the connection point, and α and β are expressed by the following equations. [Number]

[0009] In addition, the connection loss estimation method according to the present invention is a method for estimating the state of a connection point of two multimode optical fibers connected in series, inputting a conditional value into an arithmetic device, and outputting an arithmetic result obtained by substituting the conditional value into a number C1 or a number C2 and performing arithmetic operations, has been performed, wherein the arithmetic device when the conditional value is the mode field diameter (W ff1 , W ff2 ) of each of the two multimode optical fibers, substitutes the conditional value into a number C1 or a number C2, calculates the relationship between the connection loss and the amount of axial deviation (s) at the connection point for each propagation mode (LP νμ ), and uses this relationship as the arithmetic result is characterized by.

[0010] The arithmetic device of the connection loss estimation device according to the present invention when the conditional value is the mode field diameter (W ff1 , W ff2 ) and the order (ν, μ) of the propagation mode (LP νμ ), substitutes the conditional value into a number C1 or a number C2, calculates the relationship between the connection loss and the amount of axial deviation (s) for the propagation mode (LP νμ ) of the order (ν, μ), and can use this relationship as the arithmetic result.

[0011] The calculation device of the connection loss estimation device according to the present invention is The condition value is the mode field diameter (W ff1 ,W ff2 ), the aforementioned propagation mode (LP νμ When the order of (ν,μ) and the amount of axial displacement (s) are as follows, Substitute the above condition value into number C1 or number C2, and determine the propagation mode (LP) of the order (ν,μ). νμ The connection loss can be calculated for the aforementioned axial misalignment amount (s), and this connection loss can be used as the calculation result.

[0012] The connection loss estimation device according to the present invention calculates the propagation mode (LP) of a desired order (ν,μ) by substituting condition values ​​into a coupling efficiency approximation formula (number C1 or number C2) derived from the overlap integral of a higher-order Gaussian function. νμ The connection loss of each mode is calculated. Therefore, the present invention can provide an apparatus and method that can estimate the connection loss for each propagation mode even when multimode optical fibers with different mode field diameters are connected.

[0013] The present invention is a program for causing a computer to function as the connection loss estimation device. The connection loss estimation device of the present invention can also be realized by a computer and a program, and the program can be recorded on a recording medium or provided over a network.

[0014] Furthermore, the above inventions can be combined as much as possible. [Effects of the Invention]

[0015] The present invention provides an apparatus and method that can estimate the connection loss for each propagation mode even when multi-mode optical fibers with different mode field diameters are connected. [Brief explanation of the drawing]

[0016] [Figure 1] This is a diagram illustrating the connection loss estimation device according to the present invention. [Figure 2]This figure illustrates the connection loss estimation method according to the present invention. [Figure 3] This diagram illustrates the parameters of the optical fiber used in the example. [Figure 4] This figure illustrates the comparison result between the connection loss calculated by the connection loss estimation device according to the present invention and the theoretical value. [Figure 5] This is a diagram illustrating the connection loss estimation device according to the present invention. [Modes for carrying out the invention]

[0017] Embodiments of the present invention will be described with reference to the attached drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to these embodiments. In this specification and in the drawings, components with the same reference numerals refer to the same components.

[0018] (Embodiment 1) Figure 1 is a diagram illustrating the connection loss estimation device of this embodiment. This connection loss estimation device is A device for estimating the state of the connection point of two multimode optical fibers connected in series, An arithmetic unit 11 having a number C1 or a number C2 into which a condition value is substituted, An input device 12 inputs the aforementioned conditional value to the calculation device 11, An output device 13 outputs the calculation result calculated by the arithmetic unit 11, It is equipped with.

number

number

number

number

[0019] The condition value is the mode field diameter (W) of each of at least two multimode optical fibers. ff1 ,W ff2 ) If, in two multimode optical fibers connected in series, light passing through one multimode optical fiber is input to the other multimode optical fiber, then the mode field diameter of one multimode optical fiber is W ff1 The mode field diameter of the other multimode optical fiber is W ff2 That is the case.

[0020] The input device 12 is a device that inputs conditional values ​​to the arithmetic unit 11, and is, for example, a keyboard, mouse, joystick, touch panel, microphone, scanner, camera, barcode reader, or sensor. Alternatively, it may be a storage device that inputs stored conditional values ​​to the arithmetic unit 11. Furthermore, it may be an acquisition device that acquires the mode field diameter of a multimode optical fiber. The acquisition device may be, for example, a measuring instrument that acquires the mode field diameter by actual measurement such as the far-field pattern method or the variable aperture method, or a computer that calculates the mode field diameter from the electric field distribution obtained by electromagnetic field analysis such as the finite element method.

[0021] The output device 13 is a device that outputs the calculation results performed by the arithmetic unit 11, and is, for example, a display (monitor), printer, speaker, or projector. Alternatively, it may be a storage device that stores the calculation results.

[0022] The arithmetic unit 11 is The above condition value corresponds to the mode field diameter (W) of each of the two multimode optical fibers. ff1 ,W ff2 ) when Substitute the above condition value into number C1 or number C2, and determine the propagation mode (LP νμThe apparatus is characterized by calculating the relationship between the amount of axial misalignment (s) at the connection point and the connection loss for each connection point, and using this relationship as the calculation result.

[0023] Furthermore, the arithmetic unit 11 calculates the connection loss L [dB] from the coupling efficiency η calculated using formula C1 or C2 using the following formula. L = -10log 10 (η)

[0024] Figure 2 is a diagram illustrating the operation of the arithmetic unit 11. When a condition value is input from the input device 12 (step S01), the arithmetic unit 11 substitutes the condition value into number C1 or number C2 and sets the propagation mode (LP νμ For each connection point, the relationship between the amount of axial misalignment (s) and the connection loss is calculated (step S02), and the output device 13 outputs (displays on the monitor) the relationship.

[0025] Here, we will explain the derivation of formulas C1 and C2. The coupling efficiency η at the connection point can be expressed by the following electric field overlap integral.

number

number

[0026] The meaning and units of each parameter are as follows: ν,μ: Order of the propagation mode [unitless] η: Coupling efficiency at the connection point [unitless] ψ1: Electric field distribution of light input to the connection point [V / m] ψ2: Electric field distribution of light output from the connection point [V / m] r: Radial coordinate [m] in the cross-section of the optical fiber s: Amount of axial misalignment at the connection point [m] θ: Angular coordinate [rad] in the cross-section of the optical fiber F1: Electric field distribution in far-field region [V / m] F2: Electric field distribution in far field [V / m] J0: Unitless Bessel function of the 0th order of the first kind ρ: Radial coordinate in Farfield [m] Θ: Declination coordinates in Farfield [rad] w νμ : Spot size [m] of a higher-order Gaussian function L νμー1 : Laguerre polynomial [unitless] w ff1 : Mode field radius [m] of the upstream multimode optical fiber w ff2 : Mode field radius [m] of the downstream multimode optical fiber k: An integer from 0 to μ-1 [unitless] α and β are given by formula C3.

[0027] [Examples] This embodiment compares the connection loss calculated by the connection loss estimation device with the theoretical value. The theoretical value is the connection loss calculated from the overlap integral of the electric field distribution in equation (1). In this example, the connection loss between step-index 4LP-mode optical fibers (fiber A and fiber B) with different MFDs was compared. The parameters used in the calculation are shown in Table 1 of Figure 3. The wavelength was set to 1550 nm.

[0028] Figure 4 illustrates the comparison between the connection loss calculated by the connection loss estimation device and the theoretical value. The horizontal axis represents the axial misalignment s, and the vertical axis represents the connection loss L. However, in this figure, the unit of axial misalignment s is expressed in μm. The solid line represents the theoretical connection loss for LP01 mode, the dashed line represents the theoretical connection loss for LP11 mode, the dashed line represents the theoretical connection loss for LP21 mode, and the dotted line represents the theoretical connection loss for LP02 mode. The circular plots represent the calculated connection loss for LP01 mode, the triangular plots represent the calculated connection loss for LP11 mode, the square plots represent the calculated connection loss for LP21 mode, and the diamond plots represent the calculated connection loss for LP02 mode.

[0029] As shown in Figure 4, the calculated and theoretical values ​​of the connection loss are in close agreement, confirming the validity of the calculation method used by the connection loss estimation device.

[0030] In this embodiment, the mode field diameter is input from the input device 12, and the propagation mode (LP) is input. νμ It was explained that the relationship between the amount of axial misalignment (s) at the connection point and the connection loss is output from the output device 13 for each connection point. Furthermore, it was explained that the input device 12 outputs the propagation mode (LP) in addition to the mode field diameter. νμ It goes without saying that if the order (ν,μ) of the mode is also input, the output device 13 will output the relationship between the axial misalignment (s) at the connection point and the connection loss for that propagation mode. Furthermore, if the input device 12 inputs the propagation mode (LP) in addition to the mode field diameter, it will output the relationship between the connection loss and the axial misalignment (s) at the connection point for that propagation mode. νμ It goes without saying that if the order (ν,μ) and the amount of axial misalignment (s) are also input, the output device 13 will output the connection loss at the connection point for that propagation mode.

[0031] (Embodiment 2) The arithmetic unit 11 can also be realized by a computer and a program, and the program can be recorded on a recording medium or provided via a network. Figure 5 shows a block diagram of system 100. System 100 includes a computer 105 connected to network 135.

[0032] Network 135 is a data communication network. Network 135 may be a private or public network and may include any or all of the following: (a) a personal area network covering, for example, a room; (b) a local area network covering, for example, a building; (c) a campus area network covering, for example, a campus; (d) a metropolitan area network covering, for example, a city; (e) a wide area network covering, for example, an area spanning the boundaries of a city, region, or country; or (f) the Internet. Communication is carried out via Network 135 by electronic and optical signals.

[0033] Computer 105 includes a processor 110 and memory 115 connected to the processor 110. Although computer 105 is represented as a standalone device in this specification, it is not limited to this configuration and may rather be connected to other devices not shown in the illustration in a distributed processing system.

[0034] The processor 110 is an electronic device composed of logic circuits that respond to and execute instructions.

[0035] Memory 115 is a tangible, computer-readable storage medium in which computer programs are encoded. In this regard, memory 115 stores data and instructions, i.e., program code, that are readable and executable by the processor 110 in order to control the operation of the processor 110. Memory 115 can be implemented as random access memory (RAM), a hard drive, read-only memory (ROM), or a combination thereof. One of the components of memory 115 is a program module 120.

[0036] The program module 120 includes instructions for controlling the processor 110 to execute the processes described herein. In this specification, operations are described as being performed by the computer 105 or a method or process or a subordinate process thereof, but these operations are actually performed by the processor 110.

[0037] In this specification, the term "module" refers to a functional operation that can be embodied either as a standalone component or as an integrated configuration consisting of multiple subordinate components. Therefore, the program module 120 can be implemented as a single module or as multiple modules working in coordination with one another. Furthermore, although the program module 120 is described herein as being installed in memory 115 and therefore implemented in software, it can be implemented in hardware (e.g., electronic circuitry), firmware, software, or a combination thereof.

[0038] Although the program module 120 is shown as already loaded into memory 115, it may be configured to be located on the storage device 140 so that it may be loaded into memory 115 later. The storage device 140 is a tangible, computer-readable storage medium that stores the program module 120. Examples of the storage device 140 include compact disks, magnetic tapes, read-only memory, optical storage media, hard drives or memory units consisting of multiple parallel hard drives, and Universal Serial Bus (USB) flash drives. Alternatively, the storage device 140 may be random-access memory or other types of electronic storage devices located in a remote storage system (not shown) and connected to the computer 105 via the network 135.

[0039] System 100, collectively referred to herein as data source 150, further includes data source 150A and data source 150B, which are communicated to network 135. In practice, data source 150 may include any number of data sources, i.e., one or more data sources. Data source 150 may include unstructured data and may include social media.

[0040] System 100 further includes a user device 130 operated by user 101 and connected to computer 105 via network 135. The user device 130 includes an input device such as a keyboard or a speech recognition subsystem, enabling user 101 to communicate selections of information and commands to processor 110. The user device 130 further includes an output device such as a display device, printer, or speech synthesizer. A cursor control unit, such as a mouse, trackball, or touch-sensitive screen, enables user 101 to manipulate a cursor on the display device to communicate selections of further information and commands to processor 110.

[0041] The processor 110 outputs the result 122 of the execution of the program module 120 to the user device 130. Alternatively, the processor 110 can deliver the output to a storage device 125, such as a database or memory, or to a remote device (not shown) via a network 135.

[0042] For example, the program module 120 may be a program that performs the flowchart shown in Figure 2. System 100 can then be operated as the connection loss estimation device of the present invention.

[0043] The terms "equipped with..." or "possessing..." should be interpreted as specifying the existence of the feature, complete, process, or component described herein, but not excluding the existence of one or more other features, completes, processes, or components, or groups thereof. The terms "a" and "an" are indefinite articles and therefore do not exclude embodiments having multiple versions thereof.

[0044] (Other embodiments) Furthermore, this invention is not limited to the above embodiments, and can be implemented with various modifications without departing from the spirit of the invention. In short, this invention is not limited to the above embodiments as they are, and can be implemented by modifying its components without departing from the spirit of the invention.

[0045] Furthermore, various inventions can be formed by appropriately combining the multiple components disclosed in the above embodiments. For example, some components may be removed from all the components shown in the embodiments. Moreover, components from different embodiments may be appropriately combined. [Explanation of Symbols]

[0046] 11: Arithmetic device 12: Input device 13: Output device 100: System 101: User 105: Computer 110: Processor 115: Memory 120: Program Module 122:Result 125: Storage device 130: User Device 135: Network 140: Storage device 150: Data source

Claims

1. A device for estimating the state of the connection point of two multimode optical fibers connected in series, An arithmetic unit having a number C1 or a number C2 into which a condition value is substituted, An input device for inputting the aforementioned conditional value to the calculation device, An output device that outputs the calculation results calculated by the aforementioned computing device, It is equipped with, The aforementioned computing device is The condition value is the mode field diameter (W) of each of the two multimode optical fibers. ｆｆ１ , W ｆｆ２ ) when Substitute the above condition value into number C1 or number C2, and the propagation mode (LP νμ ) The relationship between the amount of axial misalignment (s) at the connection point and the connection loss is calculated for each of the above connection points, and this relationship is used as the calculation result. A device characterized by the following. [Math C1] [Math C2] However, νμ LP at the connection point νμ The coupling efficiencies between modes, α and β, are expressed by the following equations. [Math C3]

2. The aforementioned computing device is The condition value is the mode field diameter (W) ｆｆ１ , W ｆｆ２ ) and the propagation mode (LP νμ When the order of ) is (ν, μ), Substitute the condition value into the numerical value C1 or the numerical value C2, and calculate the relationship between the connection loss and the axial displacement amount (s) for the propagation mode (LP νμ ), and use this relationship as the operation result The apparatus according to claim 1, characterized by the following:

3. The aforementioned computing device is The condition value is the mode field diameter (W) ｆｆ１ , W ｆｆ２ ), the propagation mode (LP νμ When the order (ν, μ) of ) and the amount of axial displacement (s) are as follows, Substitute the above condition value into number C1 or number C2, and obtain the propagation mode (LP) of the order (ν, μ) νμ ) calculate the connection loss with respect to the axial misalignment amount (s), and use the said connection loss as the calculation result. The apparatus according to claim 1, characterized by the following:

4. A method for estimating the state of the connection point of two multimode optical fibers connected in series, Inputting conditional values ​​into the calculation unit, and The aforementioned arithmetic unit outputs the calculation result obtained by substituting the condition value into the number C1 or number C2. We are doing The aforementioned computing device The condition value is the mode field diameter (W) of each of the two multimode optical fibers. ｆｆ１ , W ｆｆ２ ) when Substitute the above condition value into number C1 or number C2, and the propagation mode (LP νμ ) The relationship between the amount of axial misalignment (s) at the connection point and the connection loss is calculated for each of the above connection points, and this relationship is used as the calculation result. A method characterized by the following. [Math C1] [Math C2] However, νμ LP at the connection point νμ The coupling efficiencies between modes, α and β, are expressed by the following equations. [Math C3]

5. A program for causing a computer to function as the device described in any one of claims 1 to 3.

Images