CN1811503A - Method for producing non-linear chirp optical fibre grating for 40 Gb/S optical communication system - Google Patents
Method for producing non-linear chirp optical fibre grating for 40 Gb/S optical communication system Download PDFInfo
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Abstract
The present invention belongs to the field of optical fibre grating production technology. It is characterized by that said invention successively includes the following several steps: designing a nonlinear chirp optical fibre grating with tunable property, namely, its reflectivity and wavelength are formed into Gaussian curve change and its group delay and wavelength are formed into secondary curve change; utilizing reconstruction principle of grating to obtain reflectivity modulation function of grating, and utilizing said function to define sampling point position and exposure time, then utilizing designed result to make a nonlinear chirp optical fibre grating for 40 G b/s optical communication system.
Description
Technical Field
The technology belongs to the technical field of optical fiber communication, and particularly relates to the field of manufacturing of optical fiber gratings.
Background
Generally, the compensation of the fiber dispersion can be realized by using a dispersion compensation fiber or a dispersion compensation device, such as a dispersion compensation fiber grating, a dispersion compensation etalon, etc. The implementation method of the dispersion compensation is fixed, and once the system is designed, the compensation amount of the dispersion cannot be changed. The accumulation of chromatic dispersion is a process that changes with time, and the system is affected by many external factors, such as temperature change, pressure, etc., so as to generate dynamically changing chromatic dispersion, which requires a dynamically tunable chromatic dispersion compensation device to compensate for the changing chromatic dispersion in a monitoring and tracking manner. The implementation mode of the tunable dispersion is the core content of the dynamic tunable dispersion compensation device. There are several ways to achieve tunable dispersion, such as changing the dispersion of a fiber grating using a dynamically changing chirp generated by thermal effects in the fiber grating, adjusting the dispersion by linear superposition using variable delay curves generated by multiple etalons, etc. Among them, tunable dispersion based on nonlinear chirp is one of the attractive methods because of its simplicity and efficiency.
The time delay curve of the nonlinear chirped fiber grating is nonlinear, and the time delay of the fiber grating can be changed by heating the fiber grating, wherein when the time delay and the wavelength of the fiber grating change in a quadratic curve, the dispersion and the wavelength have a linear relationship, and the relationship curves of the time delay (group delay) and the dispersion (dispersion) and the wavelength (wavelength) are shown in fig. 1 and 2, and at the moment, the tuning control of the fiber grating can be simpler. Therefore, the nonlinear chirped fiber grating with different structures can realize better compensation of system dispersion. Since high-quality non-linearly chirped fiber gratings require high-quality non-linearly chirped templates, which are fabricated by electron beam exposure, it is difficult and expensive to obtain high-quality non-linearly chirped templates. And different nonlinear chirped fiber gratings require different nonlinear chirped phase templates, so that the design and application of the tunable device are limited.
Due to the difficulty of obtaining high quality nonlinear chirp templates, methods have emerged that employ uniform phase templates and sampled fiber grating techniques to obtain nonlinear chirp. In the invention patent of china (application No. 200410000339.8) of "design and fabrication method of tunable dispersion compensator" by zeuger, chengzhao et al in 2004, methods of obtaining an equivalent Chirped Grating Period (CGP) using a Chirped Sampling Period (CSP) by sampling a grating and implementing tuning using a precision mechanical device were proposed.
Although the method realizes the design and manufacture of the equivalent nonlinear chirped fiber grating by using the chirped phase template, the method can only control the group delay curve of the grating and cannot simultaneously control the reflectivity curve of the grating during specific design, thereby reducing the performance of the grating. In addition, the tunable dispersion compensator is tuned by a precise mechanical device, but the precise mechanical device is expensive and large in size, so that the application of the tunable dispersion compensator is limited to a certain extent.
Disclosure of Invention
The invention aims to break through the prior art and overcome the defects of the prior art, provides a brand new method for designing and manufacturing a special sampling fiber grating with equivalent nonlinear chirp effect, and adopts a new mode to tune the grating so as to realize tunable dispersion compensation. The fiber grating adopts a uniform template design, and realizes the simultaneous control of a group delay curve and a reflectivity curve through the reconstruction and the equivalence of the grating. Then, the surface of the manufactured fiber grating is subjected to uniform metal coating, and the central wavelength of the grating is moved by using the heat effect generated when current passes through the metal coating, so that the compensation amount of chromatic dispersion is controlled.
We use the-1 order group delay profile of the sampled grating reflection peak for dispersion compensation.
The reflection characteristics of the designed grating are as follows:
reflectance curve:
group delay curve: τ (λ) ═ a (λ - λ)0)2+b(λ-λ0)+c (2)
Wherein R (λ) is the reflectivity of the grating; λ is the wavelength of the light wave; lambda [ alpha ]01553.5mm is taken as the central wavelength; b is the 3dB bandwidth of the grating reflection spectrum, and is taken as 2 nm; τ (λ) is the group delay of the grating; a. b and c are design tuning parameters of the compensator, and a is-100 ps/nm2B-300 ps/nm, c-900 ps; and m is a super-Gaussian apodization coefficient, and is taken as 4. The group delay and the wavelength of the grating are changed in a quadratic curve mode, and the dispersion and the wavelength are in a linear relation, so that the tuning control of the grating can be simpler and more stable. In addition, in the design process of the grating, the group delay characteristic and the reflectivity characteristic are simultaneously considered, the common control of the group delay characteristic and the reflectivity characteristic is realized, and a relatively flat reflection band is obtained, so that the grating with higher performance can be obtained.
Obtaining the alternating refractive index modulation function of the grating by utilizing the Fourier transform relation between the alternating refractive index modulation function and the reflection characteristic of the grating:
wherein, <math> <mrow> <mi>θ</mi> <mo>=</mo> <msubsup> <mo>∫</mo> <mn>0</mn> <mi>λ</mi> </msubsup> <mfrac> <mrow> <mn>2</mn> <mi>π</mi> </mrow> <msup> <msub> <mi>λ</mi> <mn>0</mn> </msub> <mn>2</mn> </msup> </mfrac> <mi>τ</mi> <mrow> <mo>(</mo> <msup> <mi>λ</mi> <mo>′</mo> </msup> <mo>)</mo> </mrow> <mi>d</mi> <msup> <mi>λ</mi> <mo>′</mo> </msup> <mo>,</mo> </mrow> </math> <math> <mrow> <mi>σ</mi> <mo>=</mo> <mfrac> <mrow> <mn>2</mn> <mi>nπ</mi> </mrow> <mi>λ</mi> </mfrac> <mo>-</mo> <mfrac> <mi>π</mi> <msub> <mi>Λ</mi> <mn>0</mn> </msub> </mfrac> <mo>,</mo> </mrow> </math> Λ0＝λ0and/2 n, n is the average refractive index of the grating.
Writing ac (z) as a complex exponential function:
Ac(z)＝A(z)exp[j*(z)] (4)
the refractive index modulation is realized by using a sampling grating, and the position z of each sampling point iskCalculated from equation (5):
wherein, P is a sampling parameter, and is usually 0.12 mm; k denotes the kth sampling point of the sampled grating, k being 1, 2, 3.
Exposure time T of each sampling pointkDetermined by equation (6):
wherein T ismaxFor maximum exposure time of a sample point, T is usually takenmax＝100s；max{A(zk) Denotes all the sampling points zkRefractive index modulation A (z)k) Maximum value of (2).
The design method of the tunable dispersion compensator described in the invention is characterized in that the design method sequentially comprises the following steps:
(1) designing a non-linear chirped grating with tunable characteristics, namely, reflectivity and wavelength are changed in a superss curve way, and group delay and wavelength are changed in a quadratic curve way, wherein the reflection characteristics of the grating are as follows:
τ(λ)＝a(λ-λ0)2+b(λ-λ0)+c
wherein R (λ) is the reflectivity of the grating; λ is the wavelength of the light wave; lambda [ alpha ]0Setting the central wavelength as a set value; b is the 3dB bandwidth of the grating reflection spectrum, and the unit is nm; tau (lambda) is the group delay of the grating, and the unit is ps; a, b and c areThe unit of the parameter, the set value and a is ps/nm2The units of b are ps/nm and the units of c are ps.
(2) According to the reflection characteristic of the grating, the refractive index modulation function of the grating is obtained by utilizing the reconstruction principle of the grating, and the refractive index modulation function of the grating is calculated by the following formula:
wherein z is the axial length of the optical fiber; Δ n (z) is the refractive index modulation function of the grating; lambda0The refractive index modulation period of the grating is determined by the central wavelength of the grating: lambda0＝λ0N is the average refractive index of the grating,
ac (z) the ac index modulation function, called the grating, can be calculated from:
wherein, <math> <mrow> <mi>θ</mi> <mo>=</mo> <msubsup> <mo>∫</mo> <mn>0</mn> <mi>λ</mi> </msubsup> <mfrac> <mrow> <mn>2</mn> <mi>π</mi> </mrow> <msup> <msub> <mi>λ</mi> <mn>0</mn> </msub> <mn>2</mn> </msup> </mfrac> <mi>τ</mi> <mrow> <mo>(</mo> <msup> <mi>λ</mi> <mo>′</mo> </msup> <mo>)</mo> </mrow> <mi>d</mi> <msup> <mi>λ</mi> <mo>′</mo> </msup> <mo>,</mo> </mrow> </math> <math> <mrow> <mi>σ</mi> <mo>=</mo> <mfrac> <mrow> <mn>2</mn> <mi>nπ</mi> </mrow> <mi>λ</mi> </mfrac> <mo>-</mo> <mfrac> <mi>π</mi> <msub> <mi>Λ</mi> <mn>0</mn> </msub> </mfrac> </mrow> </math>
writing ac (z) in complex exponential form as: ac (z) ═ A (z) exp [ j (z) ]
Wherein Ac (z) and A (z) and (z) are obtained by computer numerical calculation based on the designed reflection characteristics of the grating in step (1).
(3) Sampling point position z of sampling gratingkIs determined by the following equation:
wherein, P is a sampling parameter, and is usually 0.15 mm; k denotes the kth sampling point of the sampled grating, k being 1, 2, 3. Exposure time T of each sampling pointkIs determined by the following formula:
wherein T ismaxFor maximum exposure time of a sample point, T is usually takenmax100 seconds; max { A (z)k) Denotes all the sampling points
zkRefractive index modulation A (z)k) Maximum value of (2).
The difference between the design and manufacture method of the invention and the design and manufacture method of the tunable dispersion compensator is that:
the invention realizes the common control of the grating group delay curve and the reflectivity curve through the equivalence and reconstruction of the grating, thereby obtaining the fiber grating with ideal reflection characteristic. In addition, in the process of realizing the fiber grating tuning, a precise mechanical device is not adopted for tuning, but a method of uniformly coating a film on the surface of the grating is adopted, and the dispersion of the grating is adjusted by utilizing the thermal effect. The design and the manufacturing method not only can simplify the manufacturing process of the grating, but also greatly reduce the cost of the tunable dispersion compensator and reduce the volume of the tunable dispersion compensator.
The tunable dispersion compensator is characterized by comprising the following steps in sequence:
(1) carrying out hydrogen loading treatment on a common optical fiber and stripping a section of coating layer;
(2) fixing the optical fibers on the uniform template and enabling the optical fibers to be close to the uniform template;
(3) adjusting the output of the laser to 50mW of optical power;
(4) adjusting the light path to make the light spot reflected by the scanning reflector irradiate on the fiber core of the optical fiber;
(5) opening a scanning mobile platform and a laser control program of a microcomputer, and inputting and setting the following parameters:
exposure point position (given by equation (5)):
exposure time (given by equation (6)): <math> <mrow> <msub> <mi>T</mi> <mi>k</mi> </msub> <mo>=</mo> <msub> <mi>T</mi> <mi>max</mi> </msub> <mo>·</mo> <mfrac> <mrow> <mi>A</mi> <mrow> <mo>(</mo> <msub> <mi>z</mi> <mi>k</mi> </msub> <mo>)</mo> </mrow> </mrow> <mrow> <mi>max</mi> <mo>{</mo> <mi>A</mi> <mrow> <mo>(</mo> <msub> <mi>z</mi> <mi>k</mi> </msub> <mo>)</mo> </mrow> <mo>}</mo> </mrow> </mfrac> </mrow> </math>
(6) and (5) starting the scanning platform to enable the scanning platform to operate according to the set parameters in the step (5), so that the exposed optical fiber becomes an optical fiber grating with nonlinear chirp characteristics.
(7) Placing the manufactured fiber grating in oil-removing alkali liquor, heating the fiber grating in water bath at 75 ℃ for 30 minutes, wherein the oil-removing alkali liquor is prepared by the following four solutions according to the volume ratio of 1:
sodium hydroxide: 40g/L, sodium silicate: 40g/L, sodium carbonate: 30g/L, sodium phosphate: 30g/L
(8) And (3) soaking the cleaned fiber grating in a sensitizing solution for 10 seconds, then soaking the fiber grating in an activating solution for 10 seconds, and then transferring the fiber grating into the sensitizing solution. Repeating the steps for 4-5 times until the surface of the fiber grating is dark brown. The sensitizing solution and the activating solution are prepared as follows:
sensitizing solution: stannous chloride, 30g/L, 20ml
Activating solution: palladium chloride, 0.1g/L, 20ml
(9) And putting the fiber bragg grating in a nickel plating solution, and heating the fiber bragg grating in water bath for 2 hours at 50 ℃ to cover a uniform metal nickel coating on the surface of the fiber bragg grating. The nickel plating solution is prepared as follows:
nickel sulfate: 30g/L, 35ml
Sodium pyrophosphate: 90g/L, 30ml
Sodium hypophosphite: 30g/L, 25ml
Ammonia water: 40ml/L, 5ml
(10) The fiber grating covered with the uniform metal coating is welded to the electrode and encapsulated in a metal sleeve.
(11) The RS-232 port of the computer is connected with a communication pin of the single chip microcomputer AT89C52, the digital signal output of the single chip microcomputer is controlled through the computer, and the range of binary digital signals output by the single chip microcomputer is 000000000000-111111111111.
(12) And a digital signal output pin of the singlechip is connected with a digital input pin of a DA converter MAX508, the digital signal of the singlechip is converted into an analog signal by the DA converter, and the range of the voltage analog signal output by the DA converter is 0-10V.
(13) A voltage analog signal output pin of the DA converter is connected with an input pin of a power triode (Darlington tube), and the power triode is used for carrying out power amplification on a voltage signal.
(14) And (3) connecting the output port of the power triode with the electrode in the step (10), so that the voltage at two ends of the electrode is changed through a computer, and further, the dispersion provided by the compensator is changed through the computer.
The tunable dispersion compensator is used for testing in a 40Gb/s optical communication system, and the measured power cost of an optical signal after dispersion compensation is less than 0.7dB and lower than the upper limit of the power cost of 1dB specified in a communication standard, so that the tunable dispersion compensator has quite good practical performance.
In summary, the present invention can flexibly design a high performance fiber grating according to the needs of the system and the user, and the manufacturing process of the grating is simple and reliable, and the tuning device has a simple structure and stable performance, and more importantly, the tunable dispersion compensator has a low cost and a great use potential.
Description of the drawings:
FIG. 1: designing a relation curve of Group Delay (Group Delay) and light Wavelength (wavelet) of the grating;
FIG. 2: designing a relation curve of Dispersion (Dispersion) and light Wavelength (Wavelength) of the grating;
FIG. 3: making a reflectivity curve of the grating;
FIG. 4: making a group delay curve of the grating;
FIG. 5: schematic diagram of a fiber grating manufacturing device;
FIG. 6: a tuning mechanism schematic of a tunable dispersion compensator;
FIG. 7: a control device schematic diagram of a tunable dispersion compensator;
FIG. 8: the relation curve of tunable chromatic dispersion compensator electrode voltage and provided chromatic dispersion amount;
FIG. 9: a 40Gb/s tunable dispersion compensator manufacturing flow chart.
The specific implementation example is as follows:
the manufacturing method of the tunable dispersion compensator of the invention is divided into two parts: the design of the sampling grating with the secondary time delay curve and the super-Gaussian reflectivity curve is the first one, and the manufacture of the tunable dispersion compensator is the second one. Specific embodiments are described in detail below with reference to the accompanying drawings.
Design of optical fiber grating for tunable dispersion compensator
For formula (1), take B as 2nm, λ01553.5nm, m 4; for formula (2), take a ═ 100ps/nm2，b＝-300ps/nm，c＝900。
A (z) and (z) in the AC index modulation function of the grating are obtained from equation (3) using Fourier transform.
Obtaining the kth sampling point position z of the sampling grating by using the formula (5)kAnd obtaining the exposure time T at the kth sampling point by using the formula (6)k。
The reflectivity curve and the time delay curve of the manufactured grating are respectively shown in fig. 3 and 4: the dispersion varied from-260 ps/nm to-60 ps/nm over a bandwidth of 2 nm.
Second, the fabrication of tunable dispersion compensator
The device for manufacturing the grating of this embodiment is shown in fig. 5. Wherein, the light source adopts a continuous 244nm double-frequency argon ion laser 51 (manufactured by coherent company in the United states). The scanning mirror 52 is fixed on an ESP6000 scanning mobile platform (manufactured by Newport corporation) 53, and the motion precision of the scanning mobile platform is 0.1 mm. The mirror 52 has the function of scanning and reflecting the light beam and reflects the uv light output from the laser 51 onto a uniform phase mask 54, which is 60mm in length, and the uv light passes through the phase mask and impinges on a standard hydrogen-loaded single mode fiber 55 thereunder. The ESP6000 scanning mobile platform is connected to the PIO port (not shown) of the microcomputer. The movement state (movement distance, movement time, etc.) of the mobile platform is changed by running the pre-designed driving software on the microcomputer, so that the mobile platform can run according to a certain movement rule to obtain the required fiber grating.
2. The tunable dispersion compensator is characterized by comprising the following steps in sequence:
(1) carrying out hydrogen loading treatment on a common optical fiber and stripping a section of coating layer;
(2) fixing the optical fibers on the uniform template and enabling the optical fibers to be close to the uniform template;
(3) adjusting the output of the laser to 50mW of optical power;
(4) adjusting the light path to make the light spot reflected by the scanning reflector irradiate on the fiber core of the optical fiber;
(5) opening a scanning mobile platform and a laser control program of a microcomputer, and inputting and setting the following parameters: exposure point position and exposure time.
(6) And (5) starting the scanning platform to enable the scanning platform to operate according to the set parameters in the step (5), so that the exposed optical fiber becomes an optical fiber grating with nonlinear chirp characteristics.
(7) Placing the manufactured fiber grating in oil-removing alkali liquor, heating the fiber grating in water bath at 75 ℃ for 30 minutes, wherein the oil-removing alkali liquor is prepared by the following four solutions according to the volume ratio of 1:
sodium hydroxide: 40g/L, sodium silicate: 40g/L, sodium carbonate: 30g/L, sodium phosphate: 30g/L
(8) And (3) soaking the cleaned fiber grating in a sensitizing solution for 10 seconds, then soaking the fiber grating in an activating solution for 10 seconds, and then transferring the fiber grating into the sensitizing solution. Repeating the steps for 4-5 times until the surface of the fiber grating is dark brown. The sensitizing solution and the activating solution are prepared as follows:
sensitizing solution: stannous chloride, 30g/L, 20ml
Activating solution: palladium chloride, 0.1g/L, 20ml
(9) And putting the fiber bragg grating in a nickel plating solution, and heating the fiber bragg grating in water bath for 2 hours at 50 ℃ to cover a uniform metal nickel coating on the surface of the fiber bragg grating. The nickel plating solution is prepared as follows:
nickel sulfate: 30g/L, 35ml
Sodium pyrophosphate: 90g/L, 30ml
Sodium hypophosphite: 30g/L, 25ml
Ammonia water: 40ml/L, 5ml
(10) The fiber grating covered with the uniform metal coating is welded to the electrode and encapsulated in a metal sleeve.
(11) The RS-232 port of the computer is connected with a communication pin of the single chip microcomputer AT89C52, the digital signal output of the single chip microcomputer is controlled through the computer, and the range of binary digital signals output by the single chip microcomputer is 000000000000-111111111111.
(12) And a digital signal output pin of the singlechip is connected with a digital input pin of a DA converter MAX508, the digital signal of the singlechip is converted into an analog signal by the DA converter, and the range of the voltage analog signal output by the DA converter is 0-10V.
(13) A voltage analog signal output pin of the DA converter is connected with an input pin of a power triode (Darlington tube), and the power triode is used for carrying out power amplification on a voltage signal.
(14) And (3) connecting the output port of the power triode with the electrode in the step (10), so that the voltage at two ends of the electrode is changed through a computer, and further, the dispersion provided by the compensator is changed through the computer. Wherein the relationship between the electrode Voltage (Voltage) and the dispersion provided by the compensator is shown in figure 8.
A schematic diagram of a tuning arrangement used to fabricate a tunable dispersion compensator is shown in fig. 6. The metal sleeve 61 is made of a steel material to which other main components are directly or indirectly fixed. The two electrodes are fixed at the two ends of the metal sleeve by insulating glue. The two ends of the grating 62 covered with the metal nickel layer 63 are welded on the electrodes 64, and two sections of wires 65 are led out from the two electrodes 64. The voltage between the two electrodes 64 is provided by a numerical control voltage source circuit 66, and the numerical control voltage source circuit 66 is connected with an RS232 communication port of a computer through a serial port line 67. 68 is a fiber optic splice, which in use connects 68 to an optical communication system.
A schematic diagram of the tunable dispersion compensator control is shown in fig. 7. An RS232 port 71 of the computer is connected with a digital signal input pin of a singlechip 72(AT89C52) through a serial port line 67; the single chip microcomputer 72 converts serial digital voltage data sent from the computer into parallel digital voltage data, and sends the parallel digital voltage data to a digital signal input pin of a DA converter 73(MAX508) through a digital signal output pin thereof. The DA converter 73 converts the digital signal into an analog voltage signal, and the analog voltage signal is sent to the power transistor 74 from the analog voltage output port to perform power amplification. The output pin of power transistor 74 is connected to electrode 64 by conductor 65.
The tunable dispersion compensator is used for testing in a 40Gb/s optical communication system, and the measured power cost of an optical signal after dispersion compensation is less than 0.7dB and lower than the upper limit of the power cost of 1dB specified in a communication standard, so that the tunable dispersion compensator has quite good practical performance.
In summary, the present invention can flexibly design a high performance fiber grating according to the needs of the system and the user, and the manufacturing process of the grating is simple and reliable, and the tuning device has a simple structure and stable performance, and more importantly, the tunable dispersion compensator has a low cost and a great use potential.
Claims (1)
1. The method for manufacturing the nonlinear chirped fiber grating for the 40Gb/s optical communication system is characterized by sequentially comprising the following steps of:
step 1: a sampling grating with the following reflection characteristics and group delay characteristics is designed according to the following setting parameters:
reflectance curve: <math> <mrow> <mi>R</mi> <mrow> <mo>(</mo> <mi>λ</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfrac> <mi>e</mi> <msqrt> <mn>2</mn> </msqrt> </mfrac> <mi>exp</mi> <mo>[</mo> <mo>-</mo> <msup> <mrow> <mo>(</mo> <mfrac> <mrow> <mi>λ</mi> <mo>-</mo> <msub> <mi>λ</mi> <mn>0</mn> </msub> </mrow> <mrow> <mi>B</mi> <mo>/</mo> <mn>2</mn> </mrow> </mfrac> <mo>)</mo> </mrow> <mrow> <mn>2</mn> <mi>m</mi> </mrow> </msup> <mo>]</mo> <mo>,</mo> </mrow> </math>
group delay curve: τ (λ) ═ a (λ - λ)0)2+b(λ-λ0)+c，
Wherein: r (λ) is the reflectivity of the grating,
lambda is the wavelength of the light wave,
λ0λ is set as the center wavelength0＝1553.5nm，
B is the 3dB bandwidth of the grating reflection spectrum, and B is set to be 2nm,
τ (λ) is the group delay of the grating,
a, b and c are design tuning parameters, and let a be-100 ps/nm2，b＝-300ps/nm，c＝900ps，
m＝4；
Step 2: the refractive index modulation function Δ n (z) of the sampled fiber grating was calculated by a computer based on the design parameters of step 1, with the following set parameters:
wherein z is the axial coordinate of the sampling grating,
Λ0the refractive index modulation period of the sampled grating: lambda0＝λ0/2n，
n is the average refractive index of the sampled fiber grating,
the function Ac (z) is an AC refractive index modulation function of the sampled grating, and is calculated by a computer according to the following formula:
wherein, <math> <mrow> <mi>θ</mi> <mo>=</mo> <msubsup> <mo>∫</mo> <mn>0</mn> <mi>λ</mi> </msubsup> <mfrac> <mrow> <mn>2</mn> <mi>π</mi> </mrow> <msup> <msub> <mi>λ</mi> <mn>0</mn> </msub> <mn>2</mn> </msup> </mfrac> <mi>τ</mi> <mrow> <mo>(</mo> <msup> <mi>λ</mi> <mo>′</mo> </msup> <mo>)</mo> </mrow> <mi>d</mi> <msup> <mi>λ</mi> <mo>′</mo> </msup> <mo>,</mo> <mn>0</mn> <mo>≤</mo> <msup> <mi>λ</mi> <mo>′</mo> </msup> <mo>≤</mo> <mi>λ</mi> <mo>,</mo> </mrow> </math>
l is the length of the sampled grating,
the complex exponential form of the function ac (z) is:
Ac(z)＝A(z)exp[j*(z)]；
and step 3: using the refractive index modulation function obtained in step 2 according toThe position z of each sample point is determined byk：
Wherein, P is a sampling parameter, and P is 0.12 mm;
k denotes the kth sampling point of the sampled grating, k being 1, 2, 3.;
calculating the exposure time T of each sampling point according to the following formulak：
Wherein, TmaxFor maximum exposure time of the sample point, take Tmax100 seconds;
max{A(zk) Denotes all the sampling points zkRefractive index modulation amplitude A (z)k) Maximum of (1);
and 4, step 4: the nonlinear chirped fiber grating for the 40Gb/s optical communication system is manufactured according to the following steps:
step 4.1: carrying out hydrogen loading treatment on a common optical fiber and stripping a section of coating layer;
step 4.2: fixing the optical fiber obtained in the step 4.1 on the uniform template to enable the optical fiber to be close to the uniform template;
step 4.3: adjusting the output of the laser to 50mW of optical power;
step 4.4: adjusting the light path to make the light spot reflected by the scanning reflector irradiate on the fiber core of the optical fiber;
step 4.5: opening a scanning mobile platform and a laser control program of a microcomputer, and setting and inputting the following parameters according to the calculation result in the step 3:
exposure point position: 
exposure time: <math> <mrow> <msub> <mi>T</mi> <mi>k</mi> </msub> <mo>=</mo> <msub> <mi>T</mi> <mi>max</mi> </msub> <mo>·</mo> <mfrac> <mrow> <mi>A</mi> <mrow> <mo>(</mo> <msub> <mi>z</mi> <mi>k</mi> </msub> <mo>)</mo> </mrow> </mrow> <mrow> <mi>max</mi> <mo>{</mo> <mi>A</mi> <mrow> <mo>(</mo> <msub> <mi>z</mi> <mi>k</mi> </msub> <mo>)</mo> </mrow> <mo>}</mo> </mrow> </mfrac> <mo>;</mo> </mrow> </math>
step 4.6: starting a scanning platform, enabling the platform to operate according to the parameters set in the step 4.5, and enabling the exposed optical fiber to become an optical fiber grating with nonlinear chirp characteristics;
step 4.7: placing the manufactured fiber grating in oil-removing alkali liquor, heating the fiber grating in water bath at 75 ℃ for 30 minutes, wherein the oil-removing alkali liquor is prepared by the following four solutions according to the volume ratio of 1:
sodium hydroxide: 40g/L, sodium silicate: 40g/L, sodium carbonate: 30g/L, sodium phosphate: 30 g/L;
step 4.8: soaking the cleaned fiber grating in a sensitizing solution for 10 seconds, then soaking the fiber grating in an activating solution for 10 seconds, then transferring the fiber grating into the sensitizing solution, and repeating the steps for 4-5 times until the surface of the fiber grating is dark brown; the sensitizing solution and the activating solution are prepared as follows:
sensitizing solution: 30g/L of stannous chloride, 20 ml;
activating solution: palladium chloride, 0.1g/L, 20 ml;
step 4.9: putting the fiber bragg grating in a nickel plating solution, and heating the fiber bragg grating in water bath for 2 hours at 50 ℃ to cover a uniform metal nickel coating on the surface of the fiber bragg grating; the nickel plating solution is prepared as follows:
nickel sulfate: 30g/L, 35 ml;
sodium pyrophosphate: 90g/L, 30 ml;
sodium hypophosphite: 30g/L, 25 ml;
ammonia water: 40ml/L, 5 ml;
step 4.10: welding the fiber bragg grating covered with the uniform metal coating on the electrode and packaging the fiber bragg grating in the metal sleeve;
step 4.11: connecting an RS-232 port of a computer with a communication pin of a single chip microcomputer AT89C52, and controlling the digital signal output of the single chip microcomputer through the computer, wherein the range of binary digital signals output by the single chip microcomputer is 000000000000-111111111111;
step 4.12: connecting a digital signal output pin of the singlechip with a digital input pin of a DA converter MAX508, converting the digital signal of the singlechip into an analog signal by using the DA converter, wherein the range of the voltage analog signal output by the DA converter is 0-10V;
step 4.13: connecting a voltage analog signal output pin of the DA converter with an input pin of a power triode (Darlington tube), and performing power amplification on a voltage signal by using the power triode;
step 4.14: and (4) connecting an output port of the power triode with the electrode in the step 4.10 to change the dispersion of the sampling grating by a computer.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102680150A (en) * | 2012-05-28 | 2012-09-19 | 天津亿利科能源科技发展股份有限公司 | Nonlinear chirped fiber grating two-dimensional distributed strain sensing pipeline monitor device |
| CN103616742A (en) * | 2013-12-11 | 2014-03-05 | 李智忠 | Method for fabricating chirped fiber grating |
| CN106482760A (en) * | 2015-10-14 | 2017-03-08 | 北京信息科技大学 | A kind of system of all-metal packaged fiber grating strain transducer |
| CN112255722A (en) * | 2020-09-07 | 2021-01-22 | 桂林电子科技大学 | Novel method for preparing chirped fiber Bragg grating by means of uniform grating mask plate |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1105924C (en) * | 2000-06-23 | 2003-04-16 | 清华大学 | Optical fiber grating mfg. method with chirp and apodization function adjustment |
| CN1195234C (en) * | 2002-10-25 | 2005-03-30 | 清华大学 | Method for preparing optical fiber grating with freely cutting any toe part as well as the system |
| CN1303446C (en) * | 2004-01-09 | 2007-03-07 | 清华大学 | Tunable dispersion compensator designing and making method |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102680150A (en) * | 2012-05-28 | 2012-09-19 | 天津亿利科能源科技发展股份有限公司 | Nonlinear chirped fiber grating two-dimensional distributed strain sensing pipeline monitor device |
| CN103616742A (en) * | 2013-12-11 | 2014-03-05 | 李智忠 | Method for fabricating chirped fiber grating |
| CN103616742B (en) * | 2013-12-11 | 2015-06-17 | 李智忠 | Method for fabricating chirped fiber grating |
| CN106482760A (en) * | 2015-10-14 | 2017-03-08 | 北京信息科技大学 | A kind of system of all-metal packaged fiber grating strain transducer |
| CN106482760B (en) * | 2015-10-14 | 2018-09-21 | 北京信息科技大学 | A kind of system of all-metal packaged fiber grating strain transducer |
| CN112255722A (en) * | 2020-09-07 | 2021-01-22 | 桂林电子科技大学 | Novel method for preparing chirped fiber Bragg grating by means of uniform grating mask plate |
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