High-efficiency underwater optical detector based on wavelength shift optical fiber

Abstract

The invention discloses an efficient underwater optical detector based on a wavelength shift optical fiber. The photoelectric conversion efficiency and the detection sensitivity of an underwater optical detection system are improved. The specific implementation method comprises the following steps: 1, mounting a reflector behind the WSF array to improve the absorption and conversion proportion of the detector to incident blue light; 2, a reflector is installed at the tail end of the WSF array to guide excitation green light which is propagated in the back direction to a photoelectric detector to improve the signal intensity; and thirdly, the output of the WSF array is combined into one optical fiber by the optical fiber combiner, and exciting light is converged to a working area of the photoelectric detector. The method is not only suitable for underwater wireless optical communication, but also provides important technical support for various scientific researches related to the underwater environment, including marine biology and marine physics.

Description

Technical Field

[0001] This invention belongs to the field of optical detection technology, specifically relating to a high-efficiency underwater optical detector based on wavelength-shifting optical fiber. Background Technology

[0002] The ocean covers more than 70% of the Earth's surface. Ocean exploration receives global attention due to its economic and scientific importance. Natural disasters originating from the deep sea, such as cyclones and tsunamis, are beyond human control. However, their impact can be minimized through early detection and preventative measures. Researchers can gather information about natural disasters and climate change by exploring the ocean. To understand the underwater environment, researching efficient and reliable underwater communication technologies is crucial. In recent years, Underwater Wireless Optical Communication (UWOC) has received widespread attention as a high-speed, long-range underwater wireless communication technology. However, UWOC technology still faces some challenges, such as the need for line-of-sight conditions for high-speed communication, and how even slight deviations in the relative positions of the transmitter and receiver can significantly degrade performance. The performance of UWOC links also depends on the characteristics of the light source and detector; researchers are currently working on developing high-modulation-bandwidth light sources and large-field-of-view optical detectors.

[0003] Field of view (FoV) and effective area are the main factors limiting detector performance and user equipment mobility. Traditional optical detectors have small field of view and small target areas, making them unsuitable for high-speed underwater data transmission with mobility and dynamic connectivity characteristics. The performance of a UWOC receiver can be improved by increasing the received signal strength, one approach being to add optical antennas such as lenses and compound parabolic concentrators (CPCs) in front of the detector. Optical antennas collect light over a large area and converge it onto a smaller detector target area. However, the law of conservation of optical spread means that traditional optical antennas can only increase gain by reducing FoV, limiting detector performance. Another way to improve signal strength is to increase the effective area of ​​the detector in the receiver. Large effective area detectors typically have lower bandwidth, thus limiting communication speed. Small effective area detectors, due to their smaller RC time constant, can achieve higher detection bandwidth (1 GHz), making them more desirable in fixed channel capacity scenarios. Therefore, an optical receiver combining a wide field of view, large effective area, and high detection bandwidth is urgently needed for reliable high-speed underwater data transmission. This invention proposes a high-efficiency underwater optical detector based on wavelength-shifted fiber (WSF), which simultaneously features a large field of view, a large effective area, and high bandwidth. Furthermore, it enhances optical gain, receiving power, and signal-to-noise ratio through the integration of three advanced optical technologies. Summary of the Invention

[0004] To address the limitations in detection capabilities of current underwater optical detectors caused by signal attenuation, low photon conversion efficiency, small FoV, and small effective area, this invention proposes a high-efficiency underwater optical detector based on WSF.

[0005] To solve the aforementioned technical problem, the technical solution provided by the present invention is as follows:

[0006] The detector includes a WSF array (1) with an effective area of ​​0.4 cm × 20 cm, a 4×1 fiber combiner (5) connecting four 50-cm input plastic optical fibers (POF) (6) and one 50-cm output POF (7), a WSF array end transmitter (2), and a WSF array rear reflector (3). The WSF array (1) consists of four WSFs with a diameter of 1-mm and a length of 20-cm, which are connected to the input POF (6) through fiber optic connectors (4).

[0007] The method for implementing a high-efficiency underwater wireless optical detector based on WSF according to the present invention includes the following steps:

[0008] Step 1: Combining complex WSFs into an array increases the effective area of ​​the detector.

[0009] Step 2: The WSF array is excited by incident blue light, absorbs blue photons, and re-emits them as green photons.

[0010] Step 3: Place a reflector behind the WSF array, positioned opposite the direction of the blue light incident. The reflector will reflect any unabsorbed blue light back to the WSF.

[0011] Step 4: Place a reflector at the end of the WSF array to reflect the green light propagating towards it back to the WSF.

[0012] Step 5: The 4×1 fiber combiner combines the output of the WSF array into a single fiber, thereby enhancing the signal strength and facilitating coupling to a high-bandwidth, small-target photodetector.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0014] I. This invention uses a back-coupled technology to reflect unabsorbed blue light back to the WSF array for secondary conversion via a rear reflector on the optical fiber. This back-coupled technology improves the wavelength shift conversion efficiency.

[0015] Second, this invention reflects the back-propagating green light back to the WSF array through the fiber optic end reflector, thereby improving the signal strength received by the photodetector.

[0016] Third, the detector described in this invention has a large effective area, high sensitivity, and high photon conversion efficiency, which can improve the effectiveness and stability of underwater optical detection systems. Attached Figure Description

[0017] Figure 1 This is the underwater optical detector structure based on WSF described in this invention;

[0018] Figure 2 The WSF rear reflector method described in this invention;

[0019] Figure 3 This refers to the WSF end reflector method described in this invention. Detailed Implementation

[0020] To facilitate a better understanding of the features, objectives, and advantages of the present invention described above, the following description is provided in conjunction with... Figures 1 to 3 The embodiments of the present invention will be described in detail below. It should be noted that the embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0021] Figure 1This invention illustrates a high-efficiency underwater optical detector structure based on a WSF (Wireless Fiber Optic Array), comprising a WSF array 1 with an effective area of ​​0.4 cm × 20 cm, a 4×1 fiber combiner 5 containing four 50-cm input POFs 6 and one 50-cm output POF 7, a WSF array end-emitting mirror 2, and a WSF array rear-reflector 3. The WSF array 1 consists of four WSFs with a diameter of 1 mm and a length of 20 cm, connected to the input POFs 6 via fiber optic connectors 4.

[0022] The workflow of the high-efficiency underwater optical detector based on WSF involved in the embodiments of the present invention is as follows:

[0023] Step 1: Combining complex WSFs into an array increases the effective area of ​​the detector.

[0024] Step 2: The WSF array is excited by incident blue light, absorbs blue photons, and re-emits them as green photons.

[0025] Step 3: Place a reflector behind the WSF array, positioned opposite the direction of the blue light incident. The reflector will reflect any unabsorbed blue light back to the WSF.

[0026] Step 4: Place a reflector at the end of the WSF array to reflect the green light propagating towards it back to the WSF.

[0027] Step 5: The 4×1 fiber combiner combines the output of the WSF array into a single POF, enhancing the received signal strength while coupling it to a high-bandwidth, small-target photodetector.

[0028] In this embodiment, the specific process of step one is as follows:

[0029] Four WSFs with a diameter of 1 mm and a length of 20 cm form an array with an effective area of ​​0.4 cm × 20 cm. The large effective area allows the detector to capture more light over a larger spatial area, thereby improving the overall sensitivity and receiving power of the detector.

[0030] In this embodiment, the specific process of step two is as follows:

[0031] Step 2: The WSF array is excited by incident blue light, initiating a process called photon conversion. During this process, the WSF first absorbs blue light to excite the fluorophore. The absorption of photons by the fluorophore can be described by the Beer-Lambert law:

[0032] A λ =∈ (λ) c·l

[0033] In the formula A λ Let be the absorption rate of the medium for light of wavelength λ, ∈ (λ)λ represents the fluorescence absorbance of the fluorophore to wavelength λ, c represents the concentration of the absorbing fluorophore, and l represents the diameter of the WSF. Afterward, the excited-state fluorophore returns to a lower energy state and emits photons with longer wavelengths due to the Stokes shift effect.

[0034] Δλ=λ emissiomn -λ absorption

[0035] In this embodiment, the specific process of step three is as follows:

[0036] Step 3: When photons are incident on the WSF, some photons are reflected, but most are transmitted. The number of reflected photons depends on the angle of incidence and the refractive indices of the two media. Generally, reflectivity and transmittance can be calculated using the following formulas:

[0037]

[0038] T = 1 - R

[0039] In the formula, R is the reflectivity, T is the transmittance, and n1 and n2 are the refractive indices of free space and the WSF, respectively. A mirror placed behind the WSF array reflects unabsorbed blue light back into the WSF. This reflection mechanism provides these photons with a second wavelength conversion opportunity, improving the overall light absorption ratio and photon conversion efficiency.

[0040] In this embodiment, the specific process of step four is as follows:

[0041] Step 4: Due to the isotropic emission of the excited green light, it propagates in two directions within the WSF array. A mirror placed at the end of the WSF reflects the propagating green light back into the WSF. This reflection mechanism significantly increases the green light concentration at the WSF photodetector.

[0042] In this embodiment, the specific process of step five is as follows:

[0043] The WSF array transmits the received signal to the POF (Photodetector) with lower attenuation via fiber optic connectors. A 4×1 fiber combiner can combine the output of the WSF array into a single fiber to enhance the received signal strength, while also facilitating the coupling of the signal to a high-bandwidth, small-area photodetector, enabling the detector to achieve optical detection functions with a large field of view, large effective area, and high bandwidth.

Claims

1. A high-efficiency underwater optical detector based on WSF, characterized in that: The structure includes a WSF array (1) with an effective area of ​​0.4cm × 20cm, a 4×1 fiber combiner (5) connecting four 50-cm input plastic optical fibers (POF) (6) and one 50-cm output POF (7), a WSF array end transmitter (2), and a WSF array rear reflector (3). The WSF array (1) consists of four WSFs with a diameter of 1-mm and a length of 20-cm, which are connected to the input POF (6) through fiber optic connectors (4).

2. A high-efficiency underwater optical detector based on WSF, characterized in that: The implementation method includes the following steps: Step 1: An array of complex WSFs is used to increase the effective area of ​​the detector; Step 2: The WSF array is excited by incident blue light, absorbs blue photons, and re-emits them as green photons; Step 3: A reflector is placed behind the WSF array, positioned opposite the incident direction of the blue light. The reflector reflects the unabsorbed blue light back to the WSF; Step 4: A reflector is placed at the end of the WSF array to reflect the green light propagating towards it back to the WSF; Step 5: A 4×1 fiber combiner combines the outputs of the WSF array into a single fiber, thereby enhancing the signal strength and facilitating coupling to a high-bandwidth, small-target photodetector.

3. An underwater wireless optical communication system, wherein the receiver comprises a high-efficiency underwater optical detector based on WSF as described in claims 1 and 2, characterized in that... It includes reflectors placed at the rear and end of the WSF array, as well as fiber optic connectors, 4×1 fiber optic combiners, and POFs that convert the output signal of the WSF array.

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