3D waveguide type multi-core optical fiber link monitor

Abstract

The invention discloses a 3D waveguide type multi-core optical fiber link monitor which comprises an optical chip platform with n layers of stacked waveguide structures and a photoelectric detector, n is larger than or equal to 2, and the number n of waveguide layers of the optical chip platform is equal to the number of layers of connected multi-core optical fibers. The cross section distribution of waveguides in the optical chip platform and the cross section distribution of fiber cores of the multi-core optical fiber are the same and are in one-to-one correspondence; a waveguide channel corresponding to each fiber core of the multi-core optical fiber in the optical chip platform comprises an optical fiber signal coupling fan-out module, an optical signal beam splitting module, an optical signal monitoring module and a multi-core optical fiber signal coupling fan-in module which are connected in sequence; after an optical signal of a multi-core optical fiber transmitting end is coupled by the fan-out module, a small part of the signal is separated by the beam splitting module through a waveguide coupling effect and is used for monitoring, and most of the signal is transmitted back to a transmission link through the fan-in module; and the monitoring module realizes real-time detection through a photoelectric detector. According to the invention, no extra optical fiber fan-in / fan-out module is needed, the insertion loss is low, and the device is not sensitive to polarization.

Description

Technical Field

[0001] This invention belongs to the field of optical fiber communication, and in particular relates to a 3D waveguide type multi-core optical fiber link monitor. Background Technology

[0002] Cutting-edge applications such as AI training clusters, hyperscale data center interconnects, and 5G-A base station backhauls are driving exponential growth in bandwidth demands for optical communication systems. Taking AI computing centers as an example, the bandwidth requirement for optical interconnects within a single cluster has already exceeded 100 Tbps, and this needs to double every 3-5 years. Under this demand, traditional communication systems based on single-mode fiber face severe bottlenecks: constrained by both fiber nonlinearity and Shannon's capacity theorem, the single-channel transmission rate of single-mode fiber is approaching its physical limit, and its total capacity is insufficient to meet the demands of future 10-gigabit interconnect scenarios.

[0003] To overcome the aforementioned capacity bottlenecks, space division multiplexing (SDM) technology has emerged as a new generation of optical multiplexing technology. Its core idea is to construct multiple independent spatial transmission channels within a single optical fiber to achieve parallel data transmission. Among these, multi-core fiber (MCF) has become the mainstream carrier for SDM technology implementation due to its compact structure and high compatibility with the existing optical communication industry chain. MCF designs 2-36 independent cores within a single quartz cladding, and suppresses inter-core crosstalk through reasonable refractive index distribution and spacing. This allows for a significant increase in the transmission capacity of a single optical fiber to several times to tens of times that of traditional single-mode fiber without increasing fiber laying costs or physical space occupation. Currently, multi-core fiber has been piloted in scenarios such as backbone network expansion and submarine cable transmission, and its large-scale promotion has become a key support for driving the evolution of optical communication networks towards Tb-level access and Pb-level backbone.

[0004] However, with the application of multi-core optical fibers in complex network environments, the shortcomings of their link monitoring technology have gradually become apparent. Modern optical networks have transformed from traditional "static transmission" to "intelligent scheduling and dynamic operation and maintenance," requiring real-time monitoring of key parameters such as optical power, delay, wavelength, bit error rate, and polarization state of multi-core fiber links to achieve rapid fault location, dynamic resource adjustment, and transmission quality assurance. For multi-core optical fibers, since they contain multiple sets of parallel transmission cores, existing monitoring schemes require first using a fan-out module to physically separate the signals of each core before connecting them one by one to the monitoring module. After detection, the signals are transmitted back to the multi-core optical fiber transmission link through a fan-in module. The current solution suffers from three major problems: First, the introduction of demultiplexers increases link insertion loss (typically 2-5 dB), reducing transmission distance and signal quality. Second, the number of channels in the demultiplexer and the number of monitoring modules must match the number of MCF fiber cores, causing equipment costs to increase linearly with the number of fiber cores. Third, multi-module collaborative operation increases system complexity, requiring additional synchronization system design, reducing monitoring response speed, and making it difficult to meet the "real-time, low-cost, and low-loss" monitoring requirements of intelligent optical networks. Therefore, there is an urgent need to develop a new multi-core fiber link monitoring technology that is smaller, more compact, integrated, and chip-level. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a 3D waveguide-type multi-core fiber optic link monitor. By implementing the demultiplexing function of a fiber optic fan-in / fan-out module (FIFO module) on a single optical chip, it can simultaneously perform link monitoring. Compared to complex combinations of fiber optic FIFOs and monitoring modules, this invention significantly reduces the size and volume of the multi-core fiber optic link monitor, thereby lowering costs. It also enables low-loss, polarization-insensitive chip-level monitoring covering the O / C / L bands.

[0006] The objective of this invention is achieved through the following technical solution: A 3D waveguide-type multi-core fiber optic link monitor includes an optical chip platform with an n-layer stacked waveguide structure and a photodetector, where n ≥ 2. The number of waveguide layers n in the optical chip platform is equal to the number of layers in the connected multi-core fiber. The cross-sectional distribution of the waveguides in the optical chip platform is the same as and corresponds one-to-one with the cross-sectional distribution of the fiber core of the multi-core fiber. The waveguide channel corresponding to each core of the multi-core optical fiber in the optical chip platform includes a fiber signal coupling fan-out module, an optical signal splitting module, an optical signal monitoring module, and a multi-core optical fiber signal coupling fan-in module connected in sequence. The fiber optic signal coupling fan-out module includes a tapered coupling waveguide 1 and a connecting waveguide 1 connected in sequence. It is used to couple and receive the optical signal of a single core from the transmitter of a multi-core fiber, and after separating the signal spacing on different fiber cores, transmit it to the optical signal splitting module. The optical signal beam splitting module includes a beam splitting coupling waveguide one and a connecting waveguide two connected in sequence, and a beam splitting coupling waveguide two and a connecting waveguide three connected in sequence. The beam splitting coupling waveguide one and the beam splitting coupling waveguide two form an optical beam splitter. The connecting waveguide two is used to transmit the optical signal used for monitoring to the optical signal monitoring module. The connecting waveguide three is used to transmit the remaining optical signal other than the monitoring signal to the multi-core fiber signal coupling fan-in module. The optical signal monitoring module includes a connecting waveguide four and a tapered coupling waveguide two connected in sequence, and also includes a photodetector for monitoring the parameters of the multi-core optical fiber link. The multi-core fiber signal coupling fan-in module includes a connecting waveguide five and a tapered coupling waveguide three, used to transmit the remaining optical signals, excluding those for monitoring, back to the multi-core fiber receiver link.

[0007] Furthermore, the connecting waveguide one, connecting waveguide two, connecting waveguide three, connecting waveguide four and connecting waveguide five are all straight waveguides or curved waveguides, or a combination of straight waveguides and curved waveguides.

[0008] Furthermore, the photodetector is integrated into the optical chip platform.

[0009] To reduce waveguide crossings within the layer, the waveguide channels used for monitoring are located on both sides of the optical chip platform.

[0010] To ensure that the TE mode and TM mode have approximately the same effective refractive index, thereby achieving polarization insensitivity, the refractive index of the waveguide core layer of each waveguide channel in the optical chip platform is... n 芯层 Refractive index of the cladding n 包层 The following conditions must be met: ; Furthermore, the cross-sections of the connecting waveguides 1-5 and the beam splitting coupling waveguides 1 and 2 of the optical chip platform are all squares with side lengths of 2 μm to 6 μm.

[0011] To ensure low intrusion into the original signal, the optical signal splitting module allocates 0.1% to 10% of the input optical signal to the optical signal monitoring module, while the remaining optical signal is transmitted back to the multi-core optical fiber link via the multi-core optical fiber signal coupling fan-in module.

[0012] Furthermore, the 3D waveguide-type multi-core fiber optic link monitor is suitable for monitoring optical signals in the O-band, C-band, and / or L-band.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. Significantly reduces link insertion loss and improves signal transmission quality. Existing technologies require separate fiber optic fan-in / fan-out modules to connect the multi-core fiber to the monitoring module. These modules introduce a typical insertion loss of 2-5 dB, directly reducing signal transmission distance and quality. This invention integrates the multi-core fiber signal coupling fan-in / fan-out module, the optical signal splitting module, and the optical signal monitoring module into a single optical chip. This eliminates the need for an additional fiber optic FIFO demultiplexer, structurally avoiding the high insertion loss of traditional modules. It achieves low-loss signal transmission and monitoring, effectively ensuring the transmission performance of the multi-core fiber optic link.

[0014] 2. Significantly reduces equipment costs and adapts to multi-fiber core scenarios. In existing monitoring solutions, the number of channels in the demultiplexer and the number of monitoring modules must be strictly matched to the number of cores in the multi-core optical fiber. This results in a linear increase in equipment cost with the increase in the number of cores, leading to significant cost pressure in high-core-count scenarios. This invention employs a chip-level integrated design, where all functional modules are fabricated on a single optical chip. This eliminates the need for separate fan-in / fan-out components and monitoring units for each core, breaking the linear correlation between cost and core count. This significantly reduces the overall hardware cost of the multi-core optical fiber monitoring system and is more suitable for the large-scale application of high-core-count multi-core optical fibers in the future.

[0015] 3. Simplify system structure and improve monitoring response speed Existing technologies rely on the collaborative operation of multiple modules (FIFO, monitoring module, synchronization system, etc.), requiring additional synchronization control mechanisms. This leads to high system complexity, increased potential failure points, and monitoring response delays, making it difficult to meet the real-time operation and maintenance requirements of intelligent optical networks. This invention, through an integrated architecture, integrates signal fan-in / fan-out, beam splitting, and monitoring functions into a single chip device. This reduces the physical connections and coordination between modules, simplifying the system structure, lowering maintenance difficulty, and eliminating the delays caused by multi-module synchronization. It enables rapid, real-time monitoring of key parameters of multi-core fiber optic links.

[0016] 4. Achieve polarization insensitivity and wide-band coverage, adapting to practical application scenarios. This invention improves monitoring stability by avoiding monitoring errors caused by changes in the polarization state of optical signals. Simultaneously, this 3D waveguide structure supports the effective transmission and monitoring of C-band optical signals, fully matching the mainstream operating bands of current optical communication systems, ensuring its compatibility and applicability in practical scenarios such as backbone networks and data center interconnections. Attached Figure Description

[0017] Figure 1This is a schematic diagram of the overall chip structure of the 3D waveguide-type multi-core fiber optic link monitor in an embodiment of the present invention.

[0018] Figure 2 This is a schematic diagram of the multi-core optical fiber and waveguide cross-section structure in an embodiment of the present invention.

[0019] Figure 3 This is a schematic diagram of a single-layer fiber optic link monitor structure in an embodiment of the present invention.

[0020] Figure 4 This is a schematic diagram of the structure of an optical fiber link monitor corresponding to a single fiber core in an embodiment of the present invention.

[0021] Figure 5 This is a design diagram of a 7-core fiber optic 3D waveguide type fiber optic link monitor chip in an embodiment of the present invention.

[0022] Figure 6 In the embodiments of the present invention, regarding Figure 5 Chip measurement device.

[0023] Figure 7 In the embodiments of the present invention, regarding Figure 5 The measurement results for each waveguide channel of the chip are shown in the figure. Detailed Implementation

[0024] The present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments. The purpose and effects of the present invention will become clearer. It should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0025] like Figure 1 As shown, in practical applications, this invention is used in optical fiber communication networks to monitor the signal in each core of a multi-core optical fiber in real time. Its core working principle is to first fan out the signal from multiple cores, then extract a small component of each signal and feed it into a photodetector for signal monitoring. The remaining majority of the signal components are fanned back into the existing multi-core optical fiber link, achieving fan-out and fan-in functionality. The core function is to detect the signal in the current multi-core optical fiber while minimizing the impact on the existing backbone signal.

[0026] like Figure 2 As shown, in the 3D waveguide structure of this invention, the waveguide channels between different waveguide layers are aligned in the vertical direction, or arranged according to the spatial distribution of multi-core optical fibers, to achieve matching with the spatial distribution of multi-core optical fibers. For example, in a seven-core optical fiber distribution, it can be divided into a 2-3-2 distributed 3-layer structure. Therefore, the waveguide channel structure of the waveguide chip should be designed with the same distribution as described above, and in a one-to-one correspondence.

[0027] For ease of explanation, the following description uses a single-layer, two-core structure as an example. Figure 3 As shown, two cores of the multi-core fiber in the current layer are coupled into the fiber signal coupling fan-out module of the current layer. Through waveguide structure geometry design, they are further spatially separated, thus entering the optical signal splitting module. The optical signal splitting module transmits most of the components to the multi-core fiber signal coupling fan-in module to realize the backhaul link function, and a small portion enters the optical signal detection module to realize the monitoring function. The other layers implement the same functions as the current layer, thereby realizing the fan-out, fan-in, and monitoring functions of the multi-core fiber.

[0028] The following will use single-layer and single-core examples to illustrate the function of each waveguide channel. Figure 4 As shown, the waveguide channel corresponding to each core of the multi-core optical fiber in the optical chip platform includes a fiber signal coupling fan-out module, an optical signal splitting module, an optical signal monitoring module, and a multi-core optical fiber signal coupling fan-in module connected in sequence.

[0029] The fiber optic signal coupling fan-out module includes a tapered coupling waveguide 1 and a connecting waveguide 2 connected in sequence. These are used to couple and receive single-core optical signals from the multi-core fiber transmitter, achieving the fan-out function. After separating the signal spacing on different fiber cores, the signals are transmitted to the optical signal splitting module. The wedge-shaped waveguide design is to reduce the coupling loss between each fiber core and the waveguide. The connecting waveguide 2 can be a straight waveguide, a curved waveguide, or a combination of both.

[0030] The optical signal beam splitting module includes beam splitting coupling waveguide 7 and connecting waveguide 8 connected in sequence, as well as beam splitting coupling waveguide 3 and connecting waveguide 4 connected in sequence. Beam splitting coupling waveguide 7 and beam splitting coupling waveguide 3 form an optical beam splitter. Connecting waveguide 8 is used to transmit the optical signal used for monitoring to the optical signal monitoring module. Connecting waveguide 4 is used to transmit the remaining optical signal other than the monitoring signal to the multi-core fiber signal coupling fan-in module. Figure 4 The beam-splitting coupling waveguide 7 and beam-splitting coupling waveguide 3 form a directional coupler (DC) type optical beamsplitter. Of course, the design method for optical beamsplitters is not limited to the above one; Y-branch, multimode waveguide interference (MMI), and other methods are also applicable. In specific designs, different design schemes can be selected according to actual needs. After passing through the optical beamsplitter, most of the energy enters the multi-core fiber signal coupling fan-in module through connecting waveguide 3 (4) and returns to the main link. A small portion of the energy enters the optical signal monitoring module through connecting waveguide 2 (8) to realize the beam monitoring function.

[0031] The optical signal monitoring module includes a connecting waveguide 4 (9) and a tapered coupling waveguide 2 (10) connected in sequence, and a photodetector 11 for monitoring multi-core fiber optic link parameters. The multi-core fiber optic signal coupling fan-in module includes a connecting waveguide 5 (5) and a tapered coupling waveguide 3 (6), used to transmit the remaining optical signals (excluding those monitored) back to the multi-core fiber optic receiver link. Both the optical signal monitoring module and the multi-core fiber optic signal coupling fan-in module achieve low-loss coupling with the fiber optic cable via tapered waveguides. The photodetector 11 can be a combination of fiber optic cable and photodetector, or it can be directly integrated as an on-chip detector.

[0032] Figure 5 A design scheme for a 3-layer 7-core fiber optic link monitoring chip is presented. As can be seen, to reduce waveguide crossover within the layer, the seven monitoring links are located on both sides of the 7-core fiber output. This is achieved by using waveguides with a weak refractive index contrast (1.45 / 1.47) and a symmetrical geometric design (the cross-sections of connecting waveguides 1-5 and beam-splitting coupling waveguides 1 and 2 are all square, with dimensions of 3.5 × 3.5 μm). 2 This allows for polarization insensitivity. Figure 6 A measurement schematic diagram of the aforementioned chip is provided. Figure 7 Measurement results in the C-band are presented. The measurements show that the maximum signal loss of the main channel is 5.3 dB, and the signal difference between the monitoring signal and the main channel is ~15 dB (approximately 3%). In different application scenarios, the beam splitting ratio can be adjusted within the range of 0.1% to 10% to balance monitoring sensitivity and link intrusion.

[0033] In the embodiments of this invention, low-intrusion monitoring of multi-core fiber optic link signals is achieved through reasonable design of the waveguide structure and beam splitting ratio. The backbone signal maintains low insertion loss after passing through the monitor, and the monitoring branches can acquire sufficient optical signals for link parameter detection. Without departing from the technical concept of this invention, further optimization of waveguide geometry, coupling structure, material parameters, fabrication process, reduction of processing errors, and waveguide end-face polishing can achieve even lower insertion loss and better system performance. This invention is not limited to the above embodiments; all equivalent transformations or improvements made based on the technical solution of this invention should fall within the protection scope of this invention. Different chip designs can be customized according to the number of cores in different multimode fibers and the band range used.

[0034] It will be understood by those skilled in the art that the above descriptions are merely preferred examples of the invention and are not intended to limit the invention. Although the invention has been described in detail with reference to the foregoing examples, those skilled in the art can still modify the technical solutions described in the foregoing examples or make equivalent substitutions for some of the technical features. All modifications and equivalent substitutions made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A 3D waveguide-type multi-core fiber optic link monitor, characterized in that, The monitor includes an optical chip platform with an n-layer stacked waveguide structure and a photodetector, where n ≥ 2. The number of waveguide layers n of the optical chip platform is equal to the number of layers of the connected multi-core optical fiber. The cross-sectional distribution of the waveguides in the optical chip platform is the same as and corresponds one-to-one with the cross-sectional distribution of the fiber core of the multi-core optical fiber. The waveguide channel corresponding to each core of the multi-core optical fiber in the optical chip platform includes a fiber signal coupling fan-out module, an optical signal splitting module, an optical signal monitoring module, and a multi-core optical fiber signal coupling fan-in module connected in sequence. The fiber optic signal coupling fan-out module includes a tapered coupling waveguide 1 and a connecting waveguide 1 connected in sequence. It is used to couple and receive the optical signal of a single core from the transmitter of a multi-core fiber, and after separating the signal spacing on different fiber cores, transmit it to the optical signal beam splitting module. The optical signal beam splitting module includes a beam splitting coupling waveguide one and a connecting waveguide two connected in sequence, and a beam splitting coupling waveguide two and a connecting waveguide three connected in sequence. The beam splitting coupling waveguide one and the beam splitting coupling waveguide two form an optical beam splitter. The connecting waveguide two is used to transmit the optical signal used for monitoring to the optical signal monitoring module. The connecting waveguide three is used to transmit the remaining optical signal other than the monitoring signal to the multi-core fiber signal coupling fan-in module. The optical signal monitoring module includes a connecting waveguide four and a tapered coupling waveguide two connected in sequence, and also includes a photodetector for monitoring the parameters of the multi-core optical fiber link. The multi-core fiber signal coupling fan-in module includes a connecting waveguide five and a tapered coupling waveguide three, used to transmit the remaining optical signals, excluding those for monitoring, back to the multi-core fiber receiver link.

2. The 3D waveguide-type multi-core fiber optic link monitor according to claim 1, characterized in that, The connecting waveguide 1, connecting waveguide 2, connecting waveguide 3, connecting waveguide 4 and connecting waveguide 5 are all straight waveguides or curved waveguides, or a combination of straight waveguides and curved waveguides.

3. The 3D waveguide-type multi-core fiber optic link monitor according to claim 1, characterized in that, The photodetector is integrated on the optical chip platform.

4. The 3D waveguide-type multi-core fiber optic link monitor according to claim 1, characterized in that, In the optical chip platform, waveguide channels for monitoring are located on both sides of the optical chip platform.

5. The 3D waveguide-type multi-core fiber optic link monitor according to claim 1, characterized in that, The refractive index of the waveguide core layer of each waveguide channel of the optical chip platform n 芯层 Refractive index of the cladding n 包层 The following conditions must be met: The cross-sections of the connecting waveguides 1-5 and the beam splitting coupling waveguides 1 and 2 of the optical chip platform are all squares with side lengths of 2 μm to 6 μm.

6. The 3D waveguide-type multi-core fiber optic link monitor according to claim 1, characterized in that, The optical signal splitting module allocates 0.1% to 10% of the input optical signal to the optical signal monitoring module, and the remaining optical signal is transmitted back to the multi-core optical fiber link through the multi-core optical fiber signal coupling fan-in module.

7. The 3D waveguide-type multi-core fiber optic link monitor according to claim 1, characterized in that, The 3D waveguide-type multi-core fiber optic link monitor is suitable for monitoring optical signals in the O-band, C-band, and / or L-band.

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