Integrated optics-based photodetector

Abstract

The present invention is an optical detection device that senses the difference in polarization and optical power between a plurality of input signals and senses environmental changes inside and outside an optical fiber sensor probe, and is characterized by including a plurality of optical fiber pigtail blocks contained within the optical fiber pigtail blocks in which a portion of the optical fiber is housed, an integrated optical system consisting of a number of optical elements whose interfaces with the pigtail blocks are optically bonded to each other, and a balanced optical detection element for comparing the components of a plurality of polarized lights received from the optical system.

Description

[Technical Field]

[0001] The present invention relates to optical detection devices, and more particularly to polarization change-based optical sensors and integrated optics-based optical detection devices applied in optical metrology systems to increase the signal-to-noise ratio of optical receivers. [Background technology]

[0002] Generally, balanced optical detectors are used in optical sensor systems based on optical signals. Such balanced optical detectors are very important devices for ensuring the reliability and accuracy of optical measuring instruments. Meanwhile, balanced optical detectors operate by detecting the optical power difference between two input signals to sense environmental changes inside and outside the optical fiber sensor probe. Here, maximizing the change in polarization and optical power difference between the two input signals, the reference signal and the sensing signal, helps improve the reliability of the sensor.

[0003] In particular, the conventional balanced optical detection device effectively removes noise that affects the optical power of the light source, thereby increasing the signal-to-noise ratio of the optical measurement instrument and improving the accuracy of the measurement.

[0004] Meanwhile, a polarization difference balanced photodetector is generally constructed through the alignment of bulk-type polarization splitters and beam splitter optical components, that is, conventional bulk-type optical components are optically aligned so that optical signals can be transmitted effectively.

[0005] 2, such optical alignment is performed during or after mounting on a mount 1 that supports each optical component. That is, an alignment process is performed to minimize insertion loss and minimize power reduction of the optical signal through coupling between the optical fiber 2 and the bulk optical system 3.

[0006] Meanwhile, apart from the existing mechanical optical alignment, bulk optical components are bonded using adhesives, i.e., conventionally, optical alignment between optical components is performed and then the optical components are bonded in an optimally aligned state.

[0007] However, such optical alignment using a mechanical or adhesive method has the disadvantage that it is difficult to maintain the alignment state continuously, and the optical alignment may be distorted in response to external shock or vibration, or in response to changes in temperature or humidity. Therefore, in an optical system in which optical components are mounted separately from each other, precise alignment between the optical elements is required.

[0008] Referring to FIG. 1, a conventional alignment body 22 having semicircular grooves 23, 25, and 26 formed therein for precise optical alignment is disclosed, and a technique for aligning optical components therethrough is disclosed.

[0009] However, although the alignment body 22 has the advantage of simplifying alignment between optical components, it has the troublesome problem of having to individually manufacture the alignment body 22 taking into account the shapes of existing optical components. Also, since the sizes and shapes of optical elements such as optical lenses, mirrors, and optical fibers vary depending on the alignment body 22 of different shapes, there is a problem that optical alignment of the optical components must also be performed separately. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Republic of Korea Patent Publication No. 10-1994-0017015 [Patent Document 2] Republic of Korea Patent Publication No. 10-2010-0043709 Summary of the Invention [Problem to be solved by the invention]

[0011] The present invention has been invented to solve the above-mentioned problems, and aims to provide an integrated optical system-based photodetector that minimizes changes in optical characteristics due to external vibrations or temperature changes, does not require a separate alignment process, minimizes optical loss through optical bonding, and maximizes optical transmission efficiency. [Means for solving the problem]

[0012] According to one embodiment of the present invention for achieving the above-mentioned object, there is provided an optical detection device for detecting differences in polarization and optical power between a plurality of input signals and sensing environmental changes inside and outside an optical fiber sensor probe, the optical detection device including: a plurality of optical fiber pigtail blocks housed therein a portion of the optical fiber; an integrated optical system consisting of a plurality of optical elements optically bonded to each other at their interfaces with the optical fiber pigtail blocks; and a balance optical detection element for comparing components of a plurality of polarizations received from the integrated optical system.

[0013] Preferably, the optical fiber pigtail block is made of a low-thermal expansion glass material that is insensitive to temperature changes, and the optical fiber pigtail block has a structure in which a plurality of blocks are interlocked with each other, each having a V-shaped or U-shaped groove in which the optical fiber is seated.

[0014] Preferably, the integrated optical system includes a 45-degree rotator that rotates the light source of input signal 1 by 45 degrees, a beam splitter that splits input signal 1 and input signal 2 at a 50:50 ratio, and a plurality of polarization splitters that split and cross the light sources of input signal 1 and input signal 2 through the beam splitter to separate the polarization of the signals.

[0015] Preferably, the plurality of polarization splitters are arranged on the upper and side surfaces of the beam splitter, respectively, and the boundary surfaces thereof are attached by optical bonding.

[0016] Preferably, a dummy block is provided, the dummy block being made of the same material as the beam splitters and polarization splitters or a low thermal expansion silica material, and the dummy block is disposed diagonally relative to the beam splitters, with each side optically bonded to the boundary surfaces of the plurality of polarization splitters. [Effects of the Invention]

[0017] According to the present invention, firstly, the optical components are bonded together as a single unit, and a separate process of aligning the optical block and the optical fiber is not required.

[0018] Second, by providing an integrated optical system, no boundary area is formed between optical components, minimizing light loss that occurs in existing boundary areas and fundamentally preventing misalignment in response to external shocks or vibrations, thereby improving the measurement reliability of the optical detection device.

[0019] Third, the optical loss of the output light source can be minimized, enabling stable optical detection and smooth transmission of light source and sensing optical signals.

[0020] Fourth, because it is based on an integrated optical system made of low thermal expansion glass material, it is possible to minimize changes in optical characteristics due to temperature changes. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a perspective view of a conventional alignment body for optical components. [Figure 2] FIG. 2 is a diagram showing the configuration of a conventional polarization difference balanced photodetector based on bulk optical components. [Figure 3] FIG. 3 is a schematic diagram of an integrated optics-based polarization difference balanced photodetector according to one embodiment of the present invention. [Figure 4] FIG. 4 is a plan view of the integrated optical system of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0022] The present invention will now be described in more detail with reference to the accompanying drawings. The accompanying drawings are provided as examples to fully convey the concept of the present invention to those skilled in the art. The present invention is not limited to the drawings shown below and may be embodied in other forms. Furthermore, the same reference numerals will be used throughout the specification to refer to the same components.

[0023] 3 and 4, the integrated optical system-based photodetector of the present invention includes a base 10 and a plurality of optical fiber pigtail blocks B. Each optical fiber pigtail block B has a V-shaped or U-shaped groove formed between a lower block and an upper block, each made of a low-thermal expansion glass material. The blocks are provided in an interlocking configuration with optical fibers pigtailed in the V-shaped or U-shaped groove. The optical fiber pigtail blocks B can be configured to replace a photodetector (light receiving unit) and an optical fiber collimator (light input / output unit) combined with a GRIN (distributed index lens, gradient index lens) lens, if necessary. This configuration helps to adjust the degree of alignment difficulty during optical coupling and minimize optical loss.

[0024] On the other hand, the optical fiber pigtail block B can be provided in a configuration in which terminals for input signal 1 (Reference signal 1) and input signal 2 (Sensing signal 2) are accommodated.

[0025] Specifically, the 45-degree polarization rotator 50 is disposed in front of the beam splitter 40, where the input signal 1 is incident. As a result, the input signal 1, as a signal from the light source itself, is rotated by 45 degrees through the 45-degree polarization rotator 50 to become a linearly polarized reference signal, which is then distributed 50:50 through the beam splitter 40. Alternatively, the polarization-maintaining optical fiber-based input signal 1 can be rotated 45 degrees directly through a dummy block and collimator, and the linearly polarized signal rotated 45 degrees can be input to the beam splitter 40 and distributed 50:50.

[0026] Input signal 2 (Sensing signal 2) is input as a sample signal via an optical fiber sensor probe, and the optical terminal where input signal 2 is input is connected to the beam splitter 40 so that the optical terminal where input signal 1 is received can intersect with the light source of input signal 1.

[0027] Through the beam splitter 40 thus coupled, the optical signals of input signal 1 and input signal 2 cross each other and are transmitted to the polarization splitters (30a, 30b; 30) at a 50:50 ratio. Here, the polarization splitters 30a and 30b are disposed on the top and sides of the beam splitter 40. Preferably, a dummy block 20 made of a block of low thermal expansion silica material is disposed to ensure stable coupling of the polarization splitters 30a and 30b, thereby forming an integrated optical system.

[0028] The optical system configured in this way splits the optical signals of input signal 1 and input signal 2 into P-polarized light P1 and S-polarized light S1, and P-polarized light P2 and S-polarized light S2 through polarization splitters 30a and 30b, respectively, and then branches them into four channels through optically bonded optical fiber pigtail blocks (here, B1 and B2, B3 and B4 function as input terminals for the input signal and sensing signal terminals, respectively).

[0029] In this way, in the present invention, a total of six optical fiber pigtail blocks B1 to B4, a 45-degree polarization rotator 50, a beam splitter 40, polarization splitters 30a and 30b, and a dummy block 20 are provided as an integrated optical system through optical bonding.

[0030] Next, the P-polarized (P1, P2) and S-polarized (S1, S2) components split into four channels are received by a balanced photodetector 60 for comparison between each polarization component, and an optical signal is detected through a calculation process.

[0031] Meanwhile, in the present invention, for optical bonding, one surface of each optical element constituting the integrated optical system is made to have approximately the same surface shape, and the surface roughness and surface quality are improved through polishing, and foreign matter is removed through cleaning.

[0032] This type of optical bonding is a bonding method based on intermolecular attraction (Van der Waals Force), which has the effect of eliminating the adhesive boundary area, allowing optical signals passing through optical components to be transmitted stably without damage or loss at the boundary area.

[0033] That is, optical bonding is a process in which the objects to be bonded are finished to have almost the same curvature, the surfaces are cleaned, and then they are pressed together either as is or after being wetted with water or benzene. This type of optical bonding has the characteristic that the adhesive strength gradually increases over time after bonding in a surface state, the gap between the bonding surfaces is less than 4 μm, there is almost no angle error due to bonding, and there is no distortion after bonding.

[0034] In addition, the present invention uses a low thermal expansion glass material and optical elements with the same refractive index, thereby enabling stable transmission and detection of optical signals without loss between optical elements.

[0035] Specifically, the present invention provides an integrated optical system made of low-thermal expansion glass material in constructing a polarization difference balanced photodetector. This minimizes changes in optical characteristics due to external vibrations and temperature changes. Furthermore, the polarization splitters 30a and 30b, the 45-degree polarization rotator 50, the beam splitter 40, and the optical fiber pigtail blocks B1 to B4 are optically bonded together, allowing for simple construction without the need for separate alignment between the optical blocks and the optical fibers.

[0036] In particular, the integration of such optical blocks involves processing each optical block to have a right angle and bonding them together using an optical bonding method without the need for a separate adhesive between the processed surfaces, thereby eliminating the boundary surface and minimizing the optical loss that occurs at the boundary surface.

[0037] In addition, the present invention can minimize optical loss of the output light source through smooth transmission of light source and sensing optical signals.Furthermore, by directly bonding and integrating the coupling between the optical fiber and the bulk optical element, a separate alignment process is not required and optical transmission efficiency can be maximized.

[0038] Furthermore, in existing bulk optical components, mechanical or adhesive bonding methods are used to optically align the optical components and then mechanically fix or bond them in the optimal alignment state. However, in the present invention, the optical components are bonded to each other using an optical bonding method without the use of a separate adhesive between the processed surfaces, thereby minimizing distortion (misalignment) in response to external shocks or vibrations, and optical loss and noise increases in response to changes in temperature and humidity.

[0039] Although the present invention has been described in detail or with reference to specific embodiments, the present invention is not limited to the above-described embodiments. Therefore, it will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims of the present invention without departing from the spirit and scope of the invention. The following is a summary of the claims as originally filed: [1] An optical detection device that senses the difference in polarization and optical power between multiple input signals and senses environmental changes inside and outside an optical fiber sensor probe, a plurality of optical fiber pigtail blocks each containing a portion of the optical fiber; an integrated optical system consisting of a number of optical elements optically bonded to each other at their interfaces with the optical fiber pigtail block; and a balance photodetector element for comparing components of the plurality of polarizations received from the integrated optical system. [2] The optical fiber pigtail block comprises: The integrated optical system-based photodetector device described in [1] is made of a low thermal expansion glass material and is characterized in that multiple blocks, each having a V-shaped or U-shaped groove in which the optical fiber is seated, are interlocked with each other. [3] The integrated optical system is a 45-degree rotator that rotates the light source of input signal 1 by 45 degrees; a beam splitter that splits the input signal 1 and the input signal 2 at a ratio of 50:50; [1] or [2], characterized in that it includes a plurality of polarization splitters that split and cross the light sources of the input signal 1 and the input signal 2 through the beam splitter and separate the polarization of the signals. [4] The plurality of polarization splitters include: The integrated optical system-based photodetector device described in [3] is characterized in that it is arranged on the upper and side sides of the beam splitter, and the boundary surfaces thereof are attached by optical bonding. [5] further includes a dummy block; The integrated optical system-based photodetector device described in [4] is characterized in that the dummy block is arranged diagonally relative to the beam splitter, with each side optically bonded to the boundary surface of the multiple polarization splitters, and is made of low thermal expansion silica material.

Claims

1. An optical detection device that senses a difference in polarization between a plurality of input signals and senses environmental changes inside and outside an optical fiber sensor probe, a plurality of optical fiber pigtail blocks each having a portion of an optical fiber housed therein; an integrated optical system consisting of a number of optical elements optically bonded to each other at their interfaces with the optical fiber pigtail block; a balance photodetector for comparing the components of the plurality of polarized lights received from the integrated optical system; The optical fiber pigtail block comprises: An integrated optical system-based photodetector device, characterized in that a plurality of blocks, each made of low thermal expansion silica material and having a V-shaped or U-shaped groove in which the optical fiber is seated, are interlocked with each other.

2. The integrated optical system comprises: a 45-degree rotator that rotates the light source of input signal 1 by 45 degrees; a beam splitter that splits the input signal 1 and the input signal 2 at a ratio of 50:50; 2. The integrated optics-based photodetection device of claim 1, further comprising: a plurality of polarization splitters that split and cross the light sources of said input signal 1 and said input signal 2 through said beam splitter and separate the polarizations of said signals.

3. The plurality of polarization splitters include:

3. The integrated optical system-based photodetector device according to claim 2, wherein the optical elements are disposed on the upper and side surfaces of the beam splitter, and the boundary surfaces thereof are attached by optical bonding.

4. further including a dummy block; The integrated optical system-based photodetector device of claim 3, characterized in that the dummy block is arranged diagonally with respect to the beam splitter, with each side optically bonded to the boundary surface of the plurality of polarization splitters, and is made of low thermal expansion silica material.

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