KR20170139825A - Optical interferometer structure and manufacturing method of the same and optical sensors incorporating multimode interference waveguide devices using of the same and signal processing method for the same - Google Patents

Abstract

The present invention relates to a structure for an optical interferometer, which comprises: a first Y-branch optical waveguide device which emits light entering from an SLED light source; a polarization maintaining optical fiber which transfers the light emitted from the first Y-branch optical waveguide device to a sensing unit at a distance; a quarter wave plate (QWP) which converts the light conveyed through the polarization maintaining optical fiber into two circularly polarization states; a mirror which reflects the light that has passed the QWP; an electro-optic or a magneto-optic probe which is placed between the QWP and the mirror; a second Y-branch optical waveguide device which is connected to one end of the first Y-branch optical waveguide device, and where the light reflected by the mirror enters; a polarization converter which is positioned at one side of the second Y-branch optical waveguide device, and where a portion of branched light passes; a phase modulator which is positioned at the other side of the second Y-branch optical waveguide device, and where the remaining branched light passes; a 24 MMI coupler where light that has passed two routes of the second Y-branch optical waveguide device enters; and a polarizing filter which is placed at one side of the 24 MMI coupler. In addition, among light entering the 24 MMI coupler, only light with TE substances is emitted by a multimode interference phenomenon and the polarizing filter through four optical waveguides and is converted into current by an optical detector. Therefore, the structure for an optical interferometer can remove a feedback control algorithm and a feedback control circuit for controlling an initial phase in an interferometer type optical sensor.

Description

TECHNICAL FIELD [0001] The present invention relates to a structure of an optical interferometer, a manufacturing method thereof, a multimode interference optical waveguide device-based optical sensor using the same, and a signal processing method for the optical interferometer structure and manufacturing method thereof. processing method for the same}

The present invention relates to a structure of an optical interferometer for effectively detecting a phase change of a light wave generated due to a change in a physical quantity such as a magnetic field and / or an electric field due to a current / voltage and a method for manufacturing the same, and a multimode interference optical waveguide device An optical sensor and a signal processing method therefor.

2. Description of the Related Art [0002] With the recent rapid development of various optical parts technologies, sensors for effectively measuring various physical quantities have been required. In the realization of such sensors, optical sensor technology has been applied.

Optical sensors for current measurement are generally fabricated using optical fibers, and have the advantages of converting information contained in light or light into electrical signals and detecting characteristics that are not affected by non-contact, non-destructive, high-speed and disturbance .

Particularly, the characteristic that disturbance is not received in the process of transmitting the sensing signal at a long distance through the optical fiber is gradually expanding the trend of using the optical sensor for the control measurement of the large power generation and transmission system.

On the other hand, in the optical sensor technology, the phase shift of the light wave occurs due to a very small refractive index change applied to the optical fiber due to an electric field or a magnetic field. Whether or not such a phase shift can be measured more precisely and accurately is the key .

Therefore, various studies have been made to solve the problem of polarization change caused by changes in ambient temperature or optical fiber oscillation, and US20050088662 A1 " Temperature-stabilized sensor coil and current sensor " Prior arts such as US20040101228 A1 " (Fiber-optic current sensor "; JP2007040884 A1 " Reflection type optical fiber current sensor " and the like) disclose a technique related to a sensor using a polarization maintaining optical fiber.

However, in the current sensor using the polarization maintaining optical fiber, a polarization maintaining optical fiber is indispensably required, and an optical component for controlling the polarization state is required. Therefore, the system configuration becomes complicated and the price increases.

On the other hand, when a magnetic field is applied to the optical fiber in parallel with the traveling direction of light, a circular birefringence occurs due to the Faraday effect, which causes a phase difference between the two types of circularly polarized light.

Such a phase difference shows a minute difference, and a light interferometer is required to measure the phase difference.

The optical interferometer for measuring the small phase difference includes a polarization-rotated reflection interferometer (PRRI) that detects the relative phase difference between the two linearly polarized light beams.

The PRRI is used to reduce errors caused by changes in the external environment such as temperature change and vibration around the optical sensor coil.

In the PRRI structure, minute phase differences between two polarized lights generated by current are measured using an interferometer by using two perpendicular linearly polarized lights.

However, due to the characteristics of the optical interferometer, when the initial operating point changes according to the bias voltage, the magnitude of the interference signal varies, and feedback control for maintaining the sensor operating point is indispensable. To this end, additional optical components such as a linear polarization converter, a circularly polarized light converter, an optical coupler, and a phase modulator are added, resulting in a complex structure.

US 20050088662 A1 US 20040101228 A1 JP 2007040884 A1

It is an object of the present invention to provide an optical sensor operation control algorithm for operating point control and a multimode interference optical waveguide device based optical sensor capable of stable sensing operation while simplifying control electronics.

It is another object of the present invention to provide a multi-mode interference optical waveguide device-based optical sensor capable of improving stability of an interferometer and increasing productivity of a product by manufacturing various optical components including a multi-mode interferometer on one substrate.

A polarization maintaining optical fiber for transmitting light output from the first Y-branching optical waveguide to a sensing unit located at a remote location, A quarter wave plate (QWP) for converting the light transmitted through the polarization maintaining optical fiber into two circularly polarized light states, a mirror for reflecting the light passing through the quarter wave plate (QWP) And a second Y-branching optical waveguide connected to one end of the first Y-branching optical waveguide device and receiving light reflected through the mirror, And a polarized beam splitter which is disposed on one side of the second Y-branching optical waveguide and through which part of the branched light passes; Passing A 2x4 MMI coupler into which light having passed through the two paths of the second Y-branching optical waveguide flows, and a polarization filter provided at one side of the 2x4 MMI coupler, 4 MMI coupler is characterized in that, with the multimode interference phenomenon, the light of the TE component is outputted through the four optical waveguides by the polarization filter and changed into the current through the photodetector.

In the optical sensor according to the present invention including the optical interferometer structure, the four optical signal input / output characteristic curves output through the 2 × 4 MMI coupler have phase differences of 90 °, 180 ° and 270 °, And the current / voltage signal is measured through a signal generated by combining the four optical signal output signals.

The signal processing method of the optical sensor including the structure of the optical interferometer includes the steps of: securing the operating characteristics of the optical sensor in the process of driving the phase modulator including the micro-heater to initialize the sensor; using the operating characteristics obtained from the step of securing includes the step of correcting the smiling effect which occurs depending on the initial phase state, the method comprising the correction formula to the case where the phase error _e exists, Φ

을 이용하여 보정이 이루어지는 것을 특징으로 한다.

And the correction is performed using the correction value.

A method of manufacturing an optical interferometer according to the present invention includes the steps of: forming a lower cladding layer by spin-coating a polymer-based coating material on a silicon substrate; fabricating a waveguide core pattern using a photoresist; A method of fabricating a waveguide core pattern, comprising: transferring a waveguide core pattern to a cladding layer; coating a polymer-based coating agent on the waveguide core pattern and curing the core layer to form a core layer; coating a polymer- (Cr) or gold (Au), to form a polarizing pattern; and a step of coating a ZPU series coating material on the upper side of the core layer on which the polarizing pattern is formed Depositing chromium (Cr) and gold (Au) to form a phase modulation pattern after increasing the thickness of the cladding layer, Forming a grooved line for inserting the shaded wave plate located on the waveguide, and inserting and fixing the shaded wave plate to the groove line.

According to the present invention, it is possible to eliminate the feedback control algorithm and the circuit for controlling the initial phase in the interferometer type optical sensor. In addition, the PRRI structure including the multimode interferometer is integrated on the polymer optical waveguide chip, thereby improving the stability of the optical sensor and enabling mass production of optical sensor products with a simpler structure.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing an embodiment of an optical interferometer type sensor according to the present invention; FIG.
FIG. 2 is a diagram showing a comparison of an additional characteristic curve having a 90.degree. Phase difference, which is used for eliminating a characteristic dependent on an operating point while showing a change in an output signal according to a characteristic curve of a general optical interferometer and thereby an operating point change;
FIG. 3 is a view showing a manufacturing process of the optical integrated circuit shown in FIG. 1. FIG.
FIG. 4 is a diagram illustrating a structure in which a multi-mode interference element and a delayed Mach-Zehnder interference structure are connected to each other to verify the output characteristics of the multi-mode interference element, a result of the design through the beam propagation method using the structure, Fig.
FIG. 5 illustrates output characteristics of a device fabricated with different lengths of a multimode interference device and compares the output characteristics with design results. FIG.
FIG. 6 is a diagram for explaining an output signal according to an operating point change and analysis contents thereof; FIG.
FIG. 7 is a diagram for explaining a signal processing performed by using the signal of FIG. 6 to confirm a sensor characteristic independent of an operating point change; FIG.
8 is a view for explaining the characteristics of a photocurrent sensor by applying a current without operating point adjustment.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. It is to be understood, however, that the spirit of the invention is not limited to the embodiments shown and that those skilled in the art, upon reading and understanding the spirit of the invention, may easily suggest other embodiments within the scope of the same concept.

FIG. 1 is a view showing an optical sensor structure that can be modified to measure various physical quantities according to the type of a sensor probe according to an embodiment of the optical interferometer type sensor according to the present invention. In FIG. 2, And a comparative output characteristic of an optical sensor having an additional characteristic curve having a phase difference of 90 degrees with respect to the characteristic curve.

Referring to these figures, the photocurrent sensor according to the present invention mainly includes an optical integrated circuit part 200, an electromagnetic probe 400, and a photodetector part 400 which form an optical interferometer for splitting and interfering light from the light source 100, And a photodetector 800 for detection.

The light source 100 may be an S-LED having a wide wavelength bandwidth and a short coherence length.

The optical integrated circuit part 200 is fabricated using a polymer or a silica material, and is formed by integrating a plurality of Y-branch optical waveguides, an optical coupler, a phase modulator, and the like.

The Y-branch optical waveguide is divided into a first Y-branch optical waveguide and a second Y-branch optical waveguide according to the order in which the light source is introduced, and the second Y-branch optical waveguide is divided into a first Y- It is connected at one end.

The other end of the first Y-branch optical waveguide is connected to a polarization maintaining optical fiber constituting a sensing unit. The sensing unit further includes the above-described electromagnetic probe 400, a sine wave plate 320, and a mirror 600.

In detail, a sensing part for current sensing can be formed of a Hi-Bi spun fiber fabricated by twisting an optical fiber having a high birefringence and a cylindrical sensing coil wound five times in consideration of a current measurement range.

The sensing unit for voltage sensing may be formed using an electro-optic crystal such as lithium niobate (LiNbO ₃ ), BGO, or the like.

When the linearly polarized light output from the light source 100 is input to the optical integrated circuit unit 200, the TE / TM polarized light is excited to the same magnitude, and the polarized light components in the output unit of the optical integrated circuit unit 200, And it is converted to the slow axis and fast axis components of the PM fiber connected to the PM fiber.

The converted polarized light components become orthogonal and are converted into two kinds of circularly polarized light while passing through the sine wave plate 320 provided at one side of the sensing coil part. The s-wave plate 320 may be fabricated using a photonic crystal fiber having birefringence.

The phase difference between the two circularly polarized light is generated due to the Faraday effect while the electromagnetic probe 400 is moving along the sensing coil part, and the electromagnetic probe 400 changes the optical refractive index using the electrooptic or magnetooptical effect .

The mirror 600 reflects the incoming light, and the light reflected by the mirror 600 is amplified twice in phase due to the Faraday effect.

On the other hand, the light that has been reflected back is converted into two linear polarized lights again through the sine wave plate 320 and is input to the optical integrated circuit unit 200.

In this case, since the input TE / TM components pass through the sine wave plate 320 twice in the incidence and reflection process, they are converted to TM / TE components, respectively.

As described above, light input to the optical integrated circuit unit 200 is divided into two paths in the second Y-branch optical waveguide.

A phase modulator 260 is provided in one path of the second Y-branch optical waveguide, and a Half-Waveguide Plate (HWP) 340 is provided in another path.

The phase modulator 260 changes the phase of the light wave in proportion to the heat applied to the heater in accordance with the thermo-optic (TO) effect of the polymer.

The retarder (340) is inserted into the optical integrated circuit part (200) to adjust the polarization.

On the other hand, the output terminal of the second Y-branch optical waveguide is connected by a 4x4 MMI couple.

The 4x4 MMI coupler distributes the input light to a plurality of output optical waveguides by using an interference phenomenon occurring among a plurality of modes existing inside the multi-mode optical waveguide.

In the present invention, a 2 × 4 coupler 222 'structure is used in which light is incident on the first and third input terminals of the 4 × 4 MMI couplers, thereby obtaining operating characteristics having a phase difference of 90 ° with respect to each other.

In addition, a polarizing filter 250 is provided on one side of the 2x4 MMI coupler 222 '.

The polarizing filter 250 absorbs a TM mode component that causes a strong coupling with a surface plasmon mode present on the surface of the metal thin film.

Therefore, the light entering the 2x4 MMI coupler 222 'is output through the four optical waveguides of the TE component by the polarization filter 250 together with the multimode interference phenomenon, and transmitted through the photodetector 800 Current.

On the other hand, when the phase difference between the two polarization components generated by the Faraday effect in a general Mach-Zehnder interferometer structure is given as Φ _F (t), the intensity I of the interfering signal that varies with the initial operating point Φ _b is as follows.

.......................(1)

.......................(One)

.................(2)

.................(2)

Here, I ₀ is the maximum optical output of the interference signal, and A _f is the amplitude of the phase change signal due to the Faraday effect and is expressed by the following equation (3) when the equation (2) is expanded by using a Bessel function .

......(3)

(3)

The time average power signal < I > and the amplitude signal A ₀ of the frequency component in the optical output signal are extracted as follows.

...(4)

...(4)

...(5)

... (5)

The sensor output A ₀ appears proportional to the amplitude A _F of the Faraday effect signal but is dependent on the initial operating point phase value Φ _b and must be maintained at Φ _b = п / 2 to maximize A ₀ And the characteristic curve shown in FIG. 2 (a) shows that the value of A ₀ varies with the change of the value of φ _b with respect to the same A _F.

2 (b) shows another response characteristic curve whose phase is changed by 90 degrees in order to overcome the variation of the sensor output according to the operating point.

On the other hand, the two output signal amplitudes shown through the two response characteristic curves shown above change complementarily, and a final output signal independent of the operating point can be obtained through the combination of these two signals.

In detail, the output values of the two response characteristic curves having a 90 ° phase difference can be expressed by the following equations (6) and (7).

..(6)

.. (6)

..(7)

.. (7)

Here, for the two output signals, the amplitudes A ₁ and A ₂ of the frequency components of the time-averaged powers <I ₁ >, <I ₂ > and ω are expressed by the following equations (8) to (11), respectively.

...............................(8)

...............................(8)

...............................(9)

............................... (9)

..................................(10)

................................. (10)

..................................(11)

.................................. (11)

If the value of the final sensor output A ₀ is calculated by the following equation (12) using the above equations (8) to (11), it can be seen that this value is proportional to A _F without being affected by Φ _b .

.....(12)

..... (12)

The signal processing method described above corresponds to an ideal case in which two characteristic curves have a phase difference of 90 °. In actual optical IC devices, an output signal obtained from two ports due to a manufacturing process error is exactly 90 There is a problem of not having a phase difference.

Accordingly, in the signal processing method of the optical sensor according to the present invention, the phase error phi _e is introduced into the above equations (6) and (7) to solve it.

(13) and (14) by introducing the phase error phi _e into the equations (6) and (7) in detail.

..(13)

.. (13)

..(14)

.. (14)

Therefore, <I ₁ > and <I ₂ > and A ₁ and A ₂ are expressed by the following equations (15) to (18).

.......................(15)

....................... (15)

.......................(16)

... (16)

..............................(17)

.............................. (17)

..............................(18)

.............................. (18)

When the value of the final sensor output A ₀ 'is calculated according to the following equation (19) using the equations (15) to (18), when the phase error Φ _e exists, the influence of the operating point bias phase regardless of the Φ _b it is possible to obtain a sensor output.

....................(19)

... (19)

Hereinafter, a manufacturing process of the optical interferometer according to the present invention will be described with reference to FIG.

FIG. 3 is a view showing a manufacturing process of the optical integrated circuit shown in FIG.

Referring to the drawing, the optical integrated circuit part 200 according to the present embodiment is manufactured using ZPU-440 and ZPU-455 polymers of Chemoptics Inc. having refractive indexes of 1.440 and 1.455, and a single mode waveguide is fabricated with an inverted rib structure.

The core was 6.0 ㎛ wide and 6.5 ㎛ high, and the thickness of the lateral core layer was 3.0 ㎛.

In detail, in the present invention, a step of forming a lower cladding layer 220 by spin-coating a ZPU-440 polymer, which is a polymer based coating, on a silicon substrate 210 is performed.

After forming the lower cladding layer 220 as described above, the waveguide core pattern 222 is formed using photoresist, and then dry-etched by oxygen (O ₂ ) plasma using ICP-RIE equipment to form the lower cladding layer 220 is performed.

When the waveguide core pattern 222 is transferred to the lower cladding layer 220 as described above, ZPU-455, which is a polymer-based coating agent, is coated on the waveguide core pattern 222 to a thickness of about 3 μm and cured to form a core layer 230 are formed.

When the formation of the core layer 230 is completed, ZPU-440 is coated again on the top of the core layer 230 to a thickness of about 2 탆 and chromium (Cr) and gold (Au) A step of fabricating the polarization pattern 250 is performed.

The ZPU-440 is further coated on the upper side of the core layer 230 on which the polarization pattern 250 is formed to increase the thickness of the cladding layer 220 to 8 탆 and then chromium (Cr) and gold (Au) And a step of forming a phase modulation pattern 260 is performed.

After the phase modulation pattern 260 is formed as described above, a groove line 270 is formed for inserting the phase shift plate 340, and the phase shift plate 340 is inserted and fixed to the groove line 270 Step is performed.

The grooved line 270 is formed to have a width of 30 μm by using a dicing saw. The grooved line plate 340 has an optical axis and an optical integrated circuit 200) is inserted to have a 45 ° inclination and then fixed using UV curable epoxy.

Meanwhile, in the present invention, a BPM simulation is performed to design the 2x4 MMI coupler 222 '.

More specifically, when the pitch between the optical waveguides is 14 μm or more, it is confirmed that the coupling power is 1% or less. In the 2 × 4 MMI coupler 222 ', the 4-fold image is well coupled to four output optical waveguides The width and pitch of the multi-mode optical waveguide were optimized to 70 ㎛ and the pitch between the output waveguides was 23 ㎛.

FIG. 4 illustrates a structure of a multi-mode interferometer coupled with a delayed Mach-Zehnder interferometer to verify the output characteristics of the multi-mode interferometer, a beam propagation method using the same, As shown in Fig.

In the present invention, in order to check the phase difference of the characteristic curve appearing in the output signal of the 2x4 MMI coupler 222 ', a spectral response is measured to use a delayed Mach-Zehnder interferometer structure as shown in FIG. 4 (a) , And the phase difference ΔΦ caused by the delay line is expressed by the following equation (20) according to the wavelength.

.............(20)

... (20)

For this, the wavelength interval Δλ where ΔΦ = 2п is represented as follows: Equation (21).

.................................(21)

................................. (21)

When ΔI = 106 μm due to the delay line and λ ₀ = 1550 nm, Δλ becomes about 16 nm, and the resultant wavelength as shown in FIG. 4 (b) can be obtained when the length of the MMI coupler is 5130 nm.

In the delayed MZ MMI device fabricated using the polymer optical waveguide, the ideal result was obtained when the MMI length was 5230 nm, and the resultant wavelength was as shown in FIG. 4 (c).

In addition, the relative phase difference of each signal can be calculated by analyzing the interval of the wavelengths having the minimum value in the spectrum appearing at each output stage, and the phase value shown in the fabricated MMI device has a value which is less than 2 ° at an ideal 90 ° difference .

That is, the characteristics of the manufactured MMI device have an error from the designed value. To overcome this, it is possible to manufacture a plurality of devices having different lengths on one substrate and then select the device having the best characteristics.

FIG. 5 shows an output characteristic of a device fabricated with different lengths of a multimode interference device and a comparison with a design result thereof.

In FIG. 5, it is possible to confirm the phase difference between the uniformity of the output optical power and the interference characteristic curve measured in the device in which the MMI length is different from 4950 nm to 5350 nm.

Specifically, when the MMI length is 5215 nm, the output power ratio is 1 dB or less, and the relative phase difference of the output characteristic is different by 90 degrees. At this time, it is confirmed that the error is less than 5 degrees, and the results obtained through the BPM simulation are shown in FIGS. 5 (c) and 5 (d).

It is understood that the experimental result is optimized for the longer MMI device as compared with the design value as described above because the width of the optical waveguide pattern is widened during the fabrication process.

In the present invention, in order to confirm the insertion loss of the optical integrated circuit part 200 in which the MMI optical waveguide and various optical elements are integrated, light is incident on the output part connected to the sensing coil, Power was measured.

If the measured values of MMI output light are summed together, the insertion loss is 14.2 dB, which is 3 dB for Y-branch loss, 2.3 dB for fiber-waveguide mode mismatch loss, 3.7 dB for propagation loss, 0.9 dB for groove line loss, With loss of 1.3 dB, it was confirmed that the 3 dB loss of the polarizer absorbed and disappears from the TM component.

The extinction ratio of the polarization filter was measured to be 20 dB or more, and the resistance of the thermocouple phase modulator electrode was 28 Ω.

FIG. 6 is a view for explaining an output signal according to a change in operating point and an analysis result thereof. FIG. 7 shows signal processing using the signal of FIG. 6 in order to confirm a sensor characteristic independent of an operating point change. FIG. 8 is a view for explaining the characteristics of a photocurrent sensor by applying a current without operating point adjustment. In FIG.

Referring to these figures, a triangular wave of less than 1 Hz is applied to the phase modulator 260 in order to examine the signal appearing on the optical sensor while applying a 60 Hz sinusoidal current to the electric wire passing in the direction passing through the sensing coil, So that the operating point phase of the sensor is changed.

When the phase change occurs as described above, the time average power components <I ₁ > and <I ₂ > are obtained from the optical sensor output signal as shown in FIG. 6 (a) It was confirmed that the phase difference of about 90 ° was obtained.

Figure 6 (b) shows the results of measuring the optical amplitude signals A ₁ and A ₂ proportional to the amplitude of the 60 Hz current signal. The magnitudes of A ₁ and A ₂ depend on the operating point variation, It can be confirmed that the size changes mutually.

In order to check the relative phase difference of the two characteristic curves, a Lissajous curve is drawn as shown in FIG. 6 (C), from which the phase difference between the two characteristic curves deviates by 90 ° to 11.5 ° .

In order to obtain the final sensor output signal using the values of <I ₁ > and <I ₂ > and the values of A ₁ and A ₂ , the result shown by the green line in FIG. 7 is obtained by using Equation (12) . This value has an error of more than 10% according to the change of the operating point phase φ _b. This is because the phase difference between the two characteristic curves is not exactly 90 ° due to the manufacturing error of the optical integrated circuit.

In order to solve this problem, it is seen that the result of calculation using Φ _e = 11.5 ° and the equation (19) is shown by the black line in FIG. 7, and the error of the signal is reduced.

Even after the correction considering Φ _e , the cause of the remaining error is due to the characteristics of the MMI device. In the 2 × 4 MMI, when the relative phase value between the two input signals changes, the radiation is generated, It is confirmed that it can not be.

Therefore, in order to compensate for this error, the final output signal A ₀ value according to the change of φ _b is measured and recorded in the initialization step in advance, and then the operation point is calculated using the <I ₁ > and <I ₂ > And the sensor output is calibrated once again. As a result, the RMS error of the sensor output value is maintained at 2% or less even if φ _b is changed by 2 sec or more. (See the red dot in Fig. 7)

8, in order to confirm the characteristic of the current sensor operating independently of the bias, the amount of current is increased to 80 to 900 A in the open loop state in which the operating point feedback control is not performed, and then the current is again reduced to check the sensor output signal.

As a result, it was confirmed that the RMS error was 0.2% and the peak error was ± 0.05% at 100 A or more when compared with the value measured by the electric CT.

100 Light source 200 Optical integrated circuit
210 silicon substrate 220 core cladding layer
222 Waveguide core pattern 222 '... 2 x 4 MMI coupler
230 Core layer 250 Polarizing filter
260 ......... phase modulator 270 ........ groove line
320 ........ Four wave plate 340 ........ This wave plate
400 ......... Electromagnetic probe 600 ........ Mirror
800 ........ optical output device

Claims (4)

A first Y-branch optical waveguide device for outputting light incident from the SLED light source;
A polarization maintaining optical fiber for transmitting the light output from the first Y-branch optical waveguide device to a sensing unit located at a remote location;
A quarter wave plate (QWP) for converting the light transmitted through the polarization maintaining optical fiber into two circularly polarized light states;
A mirror for reflecting light passing through the quartz wave plate (QWP);
An electro-optical or magneto-optical probe provided between the quartz wave plate (QWP) and the mirror;
A second Y-branch optical waveguide element connected to one end of the first Y-branch optical waveguide element and receiving the light reflected through the mirror;
A polarization converter positioned at one side of the second Y-branch optical waveguide and through which part of the branched light passes;
A phase modulator located at another side of the second Y-branch optical waveguide and through which the rest of the branched light passes;
A 2x4 MMI coupler into which light having passed through the two paths of the second Y-branch optical waveguide flows, and a polarization filter provided on one side of the 2x4 MMI coupler,
Wherein the light incident on the 2x4 MMI coupler is converted into a current through a photodetector by outputting only TE light beams through four optical waveguides by a polarization filter together with a multimode interference phenomenon. .
11. An optical interferometer comprising a structure of an optical interferometer according to claim 1,
The four optical signal input / output characteristic curves output through the 2 × 4 MMI coupler have phase differences of 90 °, 180 ° and 270 °,
And a current / voltage signal is measured through a signal generated by combining the four optical signal output signals. The multi-mode interference optical waveguide device-based optical sensor
A signal processing method of an optical sensor including a structure of an optical interferometer according to claim 1,
Comprising the steps of: operating a phase modulator including a micro-heater to secure the operating characteristics of the optical sensor in a process of initializing the sensor;
And correcting a small influence caused by an initial phase state by using the operation characteristics acquired through securing an operation characteristic of the optical sensor,
In the correction step, when a phase error &lt; _{RTI ID} = 0.0 &gt;

And the correction is performed by using the correction value.
Spin coating a polymeric coating material on a silicon substrate to form a lower cladding layer;
Fabricating a waveguide core pattern using a photoresist and transferring the waveguide core pattern to the lower cladding layer through dry etching;
Coating a polymer-based coating agent on the upper side of the waveguide core pattern and curing the core layer to form a core layer;
Coating a polymer-based coating material on the upper side of the core layer, and depositing the coating material so as to have different thicknesses by using a metal such as chromium (Cr) or gold (Au) to form a polarization pattern;
Coating a ZPU-based coating material on the upper side of the core layer on which the polarization pattern is formed to increase the thickness of the cladding layer, and then depositing chromium (Cr) and gold (Au) to form a phase modulation pattern;
Forming a grooved line for inserting at least a portion of the retarder positioned on the waveguide and inserting and fixing the cutoff plate to the groove line.

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