The spectral noise characteristic and relative intensity noise of an all-fibre Sagnac interferometer consisting of pump source, a WDM, a piece of Er-doped fibre, a fibre Bragg grating (FBG), an optical circulator and a 50/50 coupler, were studied over a 75C-degree range. At the probing end, a high-birefringence piece of fibre and a Peltier were employed for temperature variation. Spectral and temperature response of the noise reduction due to temperature variation was performed remotely using an Arduino micro-controller and a DS18B20 digital sensor and fed into a local area network. Optical and thermal charac-terization of the system has also been undertaken.
Light propagation through optical fibers does not only have applications in optical communications for data transmission. It also has different applications such in Medicine, Industry and other areas as pressure, temperature, stress and torsion sensors [
Groups of fibres that connect to different optical components are called optical arrays. In this research work, two optical arrays were employed: An Erbium Doped Fibre Amplifier (EDFA) and a Sagnac interferometer (SI). The two optical arrays have different optical components and these arrays were characterized optically as they are inserted into the system. Characterization results on amplified spontaneous emission (ASE) noise of the separate components were investigated. Due to harsh weather conditions in our labs, remote temperature characterization through a local area network (LAN), is very important as the user could be located far from the experiment and in this way, the birefringent fibre temperature can still be known. The proposed LAN works under a client-server architecture in order to reduce the time employed for users during the component and system characterization of temperature.
The first optical array (seen in
The main purpose of this optical array is to study the operation of each component with respect to their data sheets via spectral characterization with an optical spectrum analyser (OSA). The main optical array is shown in
The EDFAs components are shown in
The next spectral characterization will include the EDFA with an optical circulator, as shown in
According to
The setup that includes a Sagnac interferometer is shown in
Results on
so it obtains considerable amplification within the EDFA.
From the previous figure, spectral characterization of port 2 at the 50/50 coupler and port 3 of the optical circulator has been performed. Power transmitted through the SI is obtained at port 2 of the coupler, while at port 3 of the circulator, the reflected power from the interferometer is obtained. Such interferometer consists on a 50/50 coupler and 0.22 m of Hi-Bi fibre, both operating at room temperature. As it could be seen in
ASE noise can be reduced through an SI, which at first indicates the need for temperature characterization of the aforementioned SI. As shown in
The optical array presented in
L = λ 2 ( Δ λ ) ( Δ n ) (1)
where:
L = Hi-Bi fibre length, in m.
λ = Wavelength of transmitted power, in nm.
Δλ = Period of valleys in the transmitted power curve, in nm.
Δn = Difference between the slow and fast axes in the Hi-Bi.
Δ λ = ( λ 2 − λ 1 ) ⋅ n max (2)
where:
Δλ = Transmittance period, in nm.
λ 1 = Wavelength of a transmitted power valley, in nm.
λ 2 = Wavelength of an adjacent transmitted power valley, in nm.
n max = number of peaks between λ 1 and λ 2 .
Equation (2) was used to calculate the transmitted power period, as shown in Equation (3):
Δ λ = ( 1548.4 nm − 1530.3 nm ) * (2)
Δ λ = 36.2 nm (3)
Equation (1) was used to calculate the Hi-Bi fibre length, as shown in Equation (4):
L = ( 1548.4 nm ) 2 ( 36.2 nm ) ( 4.22 × 10 − 4 ) = 0.1569
L = 0.16 m (4)
The second step relies on the controlled temperature for the SI, in order to reduce most of the ASE noise, for this reason it is necessary to characterize the temperature in the SI, when temperature control is added to Hi-Bi fibre it changes its characteristics for contracting or dilating [
The SI with a DS18B20 temperature sensor and an Arduino MEGA2560 plaque inside a LAN is observed in
In order to do perform the remote measurement of temperature in an SI via LAN, the schematic shown in
First, the connectivity between the client and server inside the LAN of UNACAR is verified. If there is not connectivity, then the characterization of temperature from a remote form will not be done. In order to check the connection inside of LAN, a set of data packets were sent via internet protocol (IP) inside the LAN.
In order to secure the client-server connection and for taking the temperature measurement, the following devices were used: two computers (the first working as a client and the second as a server) the optical array called “signal amplification at 1550 nm and ASE noise reduction”, an DS18B20 digital temperature
sensor and a temperature shield to connect the temperature sensor.
The next step is to use different applications to configure the communication servers between client and server and the temperature characterization. The free software used was the following: Team Viewer for the remote connection, Xampp to up the database servers, a server of Protocol Transfer File (FTP) and apache server to visualize web pages. NetBeans IDE 8.0.2 was used to programme an app in Java. With this app the user can see the temperature characterization in a friendly screen. Sublime text2 was also used to make or edit a web page, this was used in order to make an advanced search engine, for temperature characterization data. Arduino 1.6.5 was also employed as an interface to programme the controlled board with the temperature sensor. In order to connect the DS18B20 temperature sensor to the Arduino board, a PCB circuit had to be built for the sensor to work. The Arduino sensor shown in
In order to allow the user to characterize the temperature data, Java-based app was created. The temperature data are saved in database created for this purpose. An advanced search engine based on HTML5, PHP programming language, and MySQL database server are employed for visualization of results. Finally, LAN-based remote measurements within UNACAR campus were performed along with final tests and verification procedures.
In order to perform the temperature measurement in the Hi-Bi fibre within de
SI, a print circuit was made. The circuit is connected to an Arduino MEGA2560 and a DS18B20 sensor. The circuit can be connected to up to six temperature sensors, the circuit sensor connection is presented in
As it can be seen in
sensors. The PCB is shown in
An example of the temperature measurement in the Arduino display using the temperature shield and sensors are shown in the result section.
In brief, our results include: 1) EDFA ASE noise at the reflected power measurement, 2) Optical circulator spectral characterization via ASE noise measurement at the reflected power, 3) Sagnac interferometer + optical circulator spectral characterization (with 0.22 m of Hi-Bi fibre at 27˚C) at both reflected and transmitted power, 4) Sagnac interferometer + optical circulator spectral characterization (with Hi-Bi fibre at 27˚C, 30˚C, 47˚C, 87˚C, 103˚C and 104˚C) at both reflected and transmitted power, 5) General programming and electronics design for the sensors and Arduino microcontroller and finally, 6) Local area network characterization.
The general optical array is shown in
As it can be seen in
circulator. Furthermore, an attenuation of approximately 27 dB is found at both 1530 and 1548.4 nm when comparing
power of 4.11149 mW and a pump power of 200 mA. A comparison of
We will now show the results of the optical array after it was characterized and after the temperature was applied. Such characterization was made in the output port two of the transmitted power of SI at room temperature, with power ranges from 70 mA to 100 mA and with a voltage from 1 V to 10 V. Also, the characterization is made at the output port three of the optical circulator for characterizing the reflected power at room temperature and with same power and voltage ranges.
By comparing
In Figures 17-19 the characterization shows the transmitted power in the output port number two of the SI.
The highest power in the system was obtained with a pump power of 100 mA and 8 V at 87.4˚C, as it is shown in
Figures 18-20 show a fine tuning process of the main optical array via heating of the Hi-Bi fibre. After heating the fibre, the valleys shift towards shorter wavelengths, by which one could tune maximum and minimum transmitted power levels, in order to lower the ASE noise level in the whole set up.
In Figures 21-23 the characterization was made in the output port number three of the reflection power of optical circulator with a temperature of 27˚C and adding current from 70 mA to 100 mA and with a voltage of 1 V to 10 V.
Figures 21-23 show the reflected SI power measured at port 3 of the optical circulator. Such figures are similar to
The highest power when the Hi-Bi fibre is at its highest temperature was measured after 100 mA of pump power at 47.4˚C, as shown in
In this section the temperature shield is shown. It was connected to the Arduino MEGA2560 and the DS18B20 temperature sensor. Afterwards, the Arduino MEGA2560 microcontroller was programmed to characterize the temperature in the Hi-Bi fibre.
Arduino code for 2 sensors
#include // OneWire library is imported
#include //DallasTemperature library is imported for using the DS18B20
#define Pin 40 //Pin 40 is defined
OneWire ourWire(Pin); //Se establece el pin declarado como bus para la comunicación OneWire
DallasTemperature sensors(&ourWire); //Se instancia la librería DallasTemperature
boolean key = false; //Se crean variables
int mensaje = 0;
float gc1;
float gc2;
void setup() {
delay(1000); //Se espera un tiempo de un segundo
Serial.begin(9600); //Se inicializa la comunicación serial con 9600 baudios
sensors.begin(); //Se inician los sensores
}
void loop() {
sensors.requestTemperatures(); //Prepara el sensor para la lectura
if(Serial.available()>0){ //Se crean sentencias para que se haga la toma de datos,
mensaje = Serial.read(); //cuando mensaje es = a uno se hace la toma de datos,
if(mensaje=='1'){ //cuando mensaje es = 0 se detiene y no se hace la toma de datos
key = true;
}
else{
key = false;
}
}
if(key == true){ //Si se hace la toma de datos y la llave es verdadera, entonces,
gc1 = sensors.getTempCByIndex(0); //los datos se almacenan en una variable y se imrime en pantalla
Serial.println(gc1, 1); //Se lee e imprime la temperatura en grados Celsius
gc2 = sensors.getTempCByIndex(1);
Serial.println(gc2, 1); //Se lee e imprime la temperatura en grados Celsius
delay(5000); //Se provoca un lapso de 5 segundos antes de la próxima lectura
}
}
In the previous image the temperature data is shown. This data is not user friendly, for this reason, an app was developed in Java so that the user can do the characterization on a friendly environment. The app can save data in.XML format and the automatic form to a database, it is shown in the
The optical array used in this investigation is operated with a pump laser diode of 980 nm, optical array EDFA with a Bragg grating of 1548.4 nm, circulator and SI with a Hi-Bi fibre.
The results of the ASE noise characterization were made to learn about the power of the general optical array, with the graphs the user can do comparisons as needed.
When optimizing the splices of the optical array and reducing the length of Hi-Bi fibre to 0.16 m, most of the ASE noise is removed, but if it is compared when the Hi-Bi fibre had 0.22 m, the power transmitted in 0.16 m is less, so the ASE peak noise is at 1531.8 nm. Furthermore, when the Hi-Bi fibre was reduced to 0.16 m and then only signal at 1548.4 nm was let through by the SI.
Also, in this investigation the hardware and software of a system was implemented to work with detection, measurement, storage and remote acquisition of the variable temperature in a Hi-Bi fibre of an SI into the optical array. In order to make the detection and measurement of the variable temperature into the SI, it was needed to use different approaches and platform for its programming.
This investigation can be continued by removing most of the ASE noise in the EDFA, which is possible by changing the length of erbium doped fibre and parameters used in the SI. Also changing the temperature heating or cooling in the SI to find the taller valley in order to have more power and less ASE noise in the transmission, is desirable. The measurement of the system is possible by adding more sensors and editing the code. This system can work in different applications because it can be used on different surfaces.
Authors are grateful to IPN, SIP-IPN, CIITEC-IPN, UNACAR, Universidad de Quintana Roo and CONACYT, from MEXICO and Optical Sciences Group at Twente University in the Netherlands.
The authors declare no conflicts of interest regarding the publication of this paper.
Sierra-Calderon, A., Rodriguez-Novelo, J.C., May-Alarcon, M., Ek-Ek, J.R., Alvarez-Chavez, J.A. and Offerhaus, H.L. (2018) ASE Noise Characterization of an All-Fiber Sagnac Interferometer via LAN for Remote Sensing. Open Journal of Applied Sciences, 8, 554-575. https://doi.org/10.4236/ojapps.2018.812045