Multi-core optical fiber wavelength division multiplexer

Abstract

The invention relates to the technical field of communication, and particularly discloses a multi-core optical fiber wavelength division multiplexer, which comprises a double-fiber collimation head, a first wavelength division multiplexer, a second wavelength division multiplexer and a third wavelength division multiplexer, the single-fiber collimating head comprises a single-fiber tail fiber, a second collimating lens and a second sleeve; the filter assembly comprises a filter plate and a protective sleeve; the large sleeve is used for packaging and fixing the double-fiber collimation head, the filter assembly and the single-fiber collimation head; wherein the double-fiber tail fiber and the single-fiber tail fiber are both multi-core optical fibers; a traditional single-core tail fiber is replaced by the multi-core fiber, so that a single device can synchronously process a multi-space channel and a multi-wavelength channel, the fiber core symmetrical arrangement angle of the double-fiber tail fiber is set, the rotation dislocation loss of a reflection light path is reduced, and self-alignment reflection coupling of multi-core signals is achieved without active calibration.

Description

Technical Field

[0001] The present invention belongs to the field of communication technology, and in particular relates to a multi-core optical fiber wavelength division multiplexer. Background Art

[0002] Wavelength division multiplexers (WDMs) in optical communication systems combine or decompose optical signals of different wavelengths. With the emergence of new services such as mobile internet and big data, the channel capacity of single-mode optical fibers is approaching the Shannon limit, making it increasingly difficult to meet the growing communication needs. Spatial division multiplexing (SDM) is considered an effective way to further increase channel capacity, and WDMs capable of SDM optical communication systems are essential.

[0003] Existing wavelength division multiplexers typically consist of two collimation devices and a filtering device. The optical fiber used in such a device is a standard single-core, single-mode fiber. Directly replacing single-core fiber with multi-core fiber can lead to fiber misalignment, resulting in optical signal coupling failure. Furthermore, compared to single-core fiber, the collimation of multi-core fiber is more complex. Due to the performance parameters of the collimating lens used, the spacing between the collimated light spots in a multi-core fiber and the core spacing can easily be too large or too small, ultimately resulting in high coupling loss.

[0004] Therefore, it is very necessary to provide a multi-core optical fiber wavelength division multiplexer that can be used in a space division multiplexing optical communication system. Summary of the Invention

[0005] The object of the present invention is to provide a multi-core optical fiber wavelength division multiplexer to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] Multi-core fiber wavelength division multiplexer, including:

[0008] A dual-fiber collimating head, comprising a dual-fiber pigtail, a first collimating lens, and a first sleeve;

[0009] a single-fiber collimating head, comprising a single-fiber pigtail, a second collimating lens, and a second sleeve;

[0010] Filter assembly, including filter and protective sleeve;

[0011] Large sleeve, used to encapsulate and fix the dual-fiber collimator, filter assembly and single-fiber collimator;

[0012] Wherein, the dual-fiber pigtail and the single-fiber pigtail both adopt multi-core optical fibers.

[0013] Preferably, the dual-fiber pigtail comprises two independent multi-core optical fibers, the core arrangement angles of the end faces of the two independent multi-core optical fibers are consistent, and the two multi-core optical fibers are centrally symmetrically distributed about the center of the pigtail end face.

[0014] Preferably, the core arrangement of the multi-core optical fiber end face of the single-fiber pigtail is consistent with that of the dual-fiber pigtail, and the core size and / or core spacing thereof are adjustable to reduce the coupling loss of the transmitted light signal.

[0015] Preferably, the filter is configured to reflect the selected wavelength optical signal from the first multi-core optical fiber in the dual-fiber collimator head to the corresponding core of the second multi-core optical fiber, and couple the transmitted optical signal to the corresponding core of the single-fiber collimator head.

[0016] Preferably, the multi-core optical fiber is a multi-core single-mode optical fiber, a multi-core few-mode optical fiber or a multi-core multi-mode optical fiber.

[0017] Preferably, the first collimating lens and the second collimating lens are independently selected from one of a GRIN lens, a C lens, a spherical lens, and an aspherical lens.

[0018] Preferably, the filter 31 is an optical element that can simultaneously realize the wavelength selection function of each core of a multi-core optical fiber, and has the selective transmission and reflection characteristics of a multi-wavelength window.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] By replacing the traditional single-core pigtail with a multi-core optical fiber, a single device can simultaneously process multiple spatial channels and multi-wavelength channels. By setting the symmetrical arrangement angle of the cores of the dual-fiber pigtail, the rotational misalignment loss of the reflected light path is reduced, and self-aligned reflective coupling of multi-core signals can be achieved without active calibration. At the same time, the core diameter and core distance adjustable mechanism of the single-fiber pigtail dynamically match the spatial distribution of the transmitted light spot, improving the light spot-core spacing mismatch problem caused by lens aberrations. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the structure of the wavelength division multiplexer of the present invention;

[0022] Figure 2 Schematic diagram of wavelength division multiplexing optical signal transmission of the present invention;

[0023] Figure 3 This is a schematic diagram of the arrangement of the cores of a dual-fiber pigtail multi-core optical fiber of the present invention;

[0024] Figure 4 This is a schematic diagram of the end face of a multi-core optical fiber in a single-core pigtail of the present invention, wherein the core arrangement remains unchanged. Method a means keeping the core size unchanged and changing the core spacing, and method b means keeping the core spacing unchanged and changing the core size. DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] Example 1:

[0027] See also Figure 1-Figure 4 As shown, the multi-core optical fiber wavelength division multiplexer includes:

[0028] The dual-fiber collimating head 10 includes a dual-fiber pigtail 11, a first collimating lens 12, and a first sleeve 13;

[0029] The single fiber collimating head 20 includes a single fiber pigtail 21, a second collimating lens 22 and a second sleeve 23;

[0030] The filter assembly 30 includes a filter 31 and a protective sleeve 32;

[0031] The large sleeve 40 is used to encapsulate and fix the dual-fiber collimator 10, the filter assembly 30 and the single-fiber collimator 20;

[0032] Wherein, both the dual-fiber pigtail 11 and the single-fiber pigtail 21 adopt multi-core optical fibers;

[0033] In one embodiment of the present invention, the dual-fiber pigtail 11 comprises two independent multi-core optical fibers, the core arrangement angles of the end faces of which are consistent, and the two multi-core optical fibers are centrally symmetrically distributed about the center of the pigtail end face;

[0034] In one embodiment of the present invention, the dual-fiber pigtail 11 uses two 7-core single-mode optical fibers with a core diameter of 8.2 μm and a core spacing of 42 μm. The cores are arranged as follows after end face grinding: Figure 3 As shown, the two optical fibers are installed symmetrically with respect to the center of the circle and rotated 180°;

[0035] In one embodiment of the present invention, the core arrangement of the multi-core optical fiber end face of the single-fiber pigtail 21 is consistent with that of the dual-fiber pigtail 11, and its core size and / or core spacing are adjustable to reduce the coupling loss of the transmitted light signal;

[0036] In one embodiment of the present invention, the single-fiber pigtail 21 uses the same 7-core optical fiber, but the core spacing is adjusted to 38 μm to match the transmitted beam spacing;

[0037] In one embodiment of the present invention, the filter 31 is configured to: reflect the selected wavelength optical signal from the first multi-core optical fiber in the dual-fiber collimation head 10 to the corresponding core of the second multi-core optical fiber, and couple the transmitted optical signal to the corresponding core of the single-fiber collimation head 20;

[0038] In one embodiment of the present invention, the multi-core optical fiber is a multi-core single-mode optical fiber, a multi-core few-mode optical fiber or a multi-core multi-mode optical fiber, supporting LP mode, OAM mode and other optical fiber transmission modes;

[0039] In one embodiment of the present invention, the first collimating lens 12 and the second collimating lens 22 are independently selected from one of a GRIN lens, a C lens, a spherical lens, and an aspherical lens;

[0040] In one embodiment of the present invention, the first collimating lens 12 and the second collimating lens 22 are both GRIN lenses (diameter 1.8 mm, pitch 0.24±0.01), which achieve low-aberration collimation in the C+L band (1520-1625 nm);

[0041] In one embodiment of the present invention, the filter 31 is selected from a thin film filter, a grating filter or other optical filter elements capable of achieving wavelength selection;

[0042] In one embodiment of the present invention, the filter 31 is a broadband thin film filter with a passband range of 1530-1565 nm (covering the C band), a reflection band range of 1565-1625 nm (covering the L band), and an edge roll-off slope of >3 dB / nm;

[0043] In one embodiment of the present invention, the multi-core optical fiber wavelength division multiplexer assembly process steps include:

[0044] Step 1: Coat the side of the GRIN lens 12 with UV glue model NOA81, insert it into the first sleeve 13 for UV curing, insert the dual-fiber pigtail 11 into the sleeve, adjust the air gap to 0.15mm, and monitor the reflection coupling efficiency in real time until it is greater than 99% before curing;

[0045] Step 2: Tilt the filter 31 8° and adhere it to the inner wall of the protective sleeve 32, and then attach it to the outer side of the lens of the dual-fiber collimator;

[0046] Step 3: Fix the single fiber pigtail 21 and the second collimating lens 22 in the same manner as in step 1;

[0047] Step 4: Adjust the position of the single-fiber collimator head so that the transmitted light spot coincides with the fiber core and the coupling loss is less than 0.5 dB. Install the three components into the large sleeve 40, apply glue and solidify to form an integral structure.

[0048] Example 2:

[0049] The difference from the first embodiment is that the dual-fiber pigtail 11 uses a 4-core multimode optical fiber to support the LP11 mode with a core diameter of 50 μm, and the core diameter of the single-fiber pigtail 21 is enlarged to 52 μm;

[0050] The lens selected is an aspheric lens with NA=0.25 and a focal length of 4.5mm;

[0051] The filter is selected as a grating filter with a channel spacing of 100 GHz;

[0052] After the dual-fiber pigtails are symmetrically arranged, OAM mode reflection coupling is achieved by fine-tuning the filter angle by 6°±0.5°, and the core diameter of the single-fiber pigtail is expanded by 5% to accommodate the spot broadening caused by modal dispersion;

[0053] The remaining steps are the same as those in Example 1 and will not be described in detail here.

[0054] Experimental example:

[0055] The performance of the optical fiber wavelength division multiplexer in Example 1 was tested, and the equipment selection was shown in the following table:

[0056] Device Name Model / Specifications Tunable laser source Keysight 81600B (wavelength range 1520-1620 nm) Optical power meter EXFOPM-1100 (accuracy ±0.02dB) Optical Spectrum Analyzer (OSA) Yokogawa AQ6370D (resolution 0.02nm) Multi-channel fiber optic switch DiCon16×16 MEMS switch

[0057] Insertion Loss (IL) test: The laser source output wavelength is 1550nm (the center wavelength of the filter) and the power is 0dBm. The seven cores of the dual-fiber pigtail are excited in sequence through the optical fiber switch. The output power of the reflection channel (the corresponding core of the other fiber in the dual-fiber pigtail) and the transmission channel (the corresponding core of the single-fiber pigtail) are measured respectively. The specific data are as follows:

[0058] Fiber core number Reflection channel IL (dB) Transmission channel IL (dB) 1 0.72 0.95 2 0.75 0.98 3 0.68 0.92 4 0.71 0.94 5 0.69 0.97 6 0.74 0.96 7 0.70 0.93 average 0.71 0.95

[0059] From the above, we can see that the average IL of the reflection channel is ≤ 0.8dB, and the average IL of the transmission channel is ≤ 1.0dB, which meets the design goals;

[0060] Wavelength isolation test: The laser source wavelength sweep range is 1549nm–1551nm (0.1nm step). The input fiber core is fixed. The power attenuation of the reflection channel at 1549.5nm and 1550.5nm is measured. The power attenuation of the transmission channel at 1549.5nm is measured. The specific data is as follows:

[0061] Wavelength (nm) Reflection channel attenuation (dB) Transmission channel attenuation (dB) 1549.5 >40 0.95 1550.0 0.72 40.2 1550.5 >40 0.94

[0062] As can be seen from the above, the out-of-band wavelength suppression is greater than 40dB, meeting the DWDM system requirements (ITU-T G.694.1);

[0063] Crosstalk test: Input a 1550nm / 0dBm signal to core 1, measure the output power of cores 2-7 in the reflection / transmission channels, and calculate the crosstalk. The specific data is as follows:

[0064] Interference core Reflection channel crosstalk (dB) Transmission channel crosstalk (dB) Core 2 -42.1 -41.8 Core 3 -43.5 -42.3 Core 4 -44.2 -43.7 Core 5 -42.9 -42.0 Core 6 -43.8 -41.5 Core 7 -42.5 -42.9 Worst value -41.5 -41.5

[0065] From the above, we can see that the maximum crosstalk is less than -40dB, which is better than the industry standard (typical requirement is greater than -30dB).

[0066] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A multi-core optical fiber wavelength division multiplexer, characterized in that: include: A dual-fiber collimating head (10) comprising a dual-fiber pigtail (11), a first collimating lens (12) and a first sleeve (13); A single-fiber collimating head (20) comprising a single-fiber pigtail (21), a second collimating lens (22) and a second sleeve (23); A filter assembly (30) comprising a filter (31) and a protective sleeve (32); A large sleeve (40) is used to encapsulate and fix the dual-fiber collimating head (10), the filter assembly (30) and the single-fiber collimating head (20); Wherein, the dual-fiber pigtail (11) and the single-fiber pigtail (21) both adopt multi-core optical fibers.

2. The multi-core optical fiber wavelength division multiplexer according to claim 1, wherein: The dual-fiber pigtail (11) comprises two independent multi-core optical fibers, the end face fiber cores of which are arranged at the same angle, and the two multi-core optical fibers are centrally symmetrically distributed about the center of the pigtail end face.

3. The multi-core optical fiber wavelength division multiplexer according to claim 1, wherein: The multi-core optical fiber end face core arrangement of the single-fiber pigtail (21) is consistent with that of the dual-fiber pigtail (11), and its core size and / or core spacing are adjustable, so as to reduce the coupling loss of the transmitted light signal.

4. The multi-core optical fiber wavelength division multiplexer according to claim 1, wherein: The filter (31) is configured to reflect a selected wavelength optical signal from a first multi-core optical fiber in a dual-fiber collimating head (10) to a corresponding fiber core of a second multi-core optical fiber, and couple a transmitted optical signal to a corresponding fiber core of a single-fiber collimating head (20).

5. The multi-core optical fiber wavelength division multiplexer according to claim 1, wherein: The multi-core optical fiber is a multi-core single-mode optical fiber, a multi-core few-mode optical fiber or a multi-core multi-mode optical fiber.

6. The multi-core optical fiber wavelength division multiplexer according to claim 1, wherein: The first collimating lens (12) and the second collimating lens (22) are independently selected from one of a GRIN lens, a C lens, a spherical lens, and an aspherical lens.

7. The multi-core optical fiber wavelength division multiplexer according to claim 1, wherein: The filter (31) is an optical filter element capable of achieving wavelength selection.

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