Tomi Budi Waluyo

Development of microcontroller-based acquisition and processing unit for fiber optic vibration sensor

Microcontroller based acquisition and processing unit (MAPU) has been developed to measure vibration signal from fiber optic vibration sensor. The MAPU utilizes a 32-bit ARM microcontroller to perform acquisition and processing of the input signal. The input signal is acquired with 12 bit ADC and processed using FFT method to extract frequency information. Stability of MAPU is characterized by supplying a constant input signal at 500 Hz for 29 hours and shows a stable operation. To characterize the frequency response, input signal is swapped from 20 to 1000 Hz with 20 Hz interval. The characterization result shows that MAPU can detect input signal from 20 to 1000 Hz with minimum signal of 4 mV RMS. The experiment has been set that utilizes the MAPU with singlemode-multimode-singlemode (SMS) fiber optic sensor to detect vibration which is induced by a transducer in a wooden platform. The experimental result indicates that vibration signal from 20 to 600 Hz has been successfully detected. Due to the limitation of the vibration source used in the experiment, vibration signal above 600 Hz is undetected.

Using a Telecommunication-Grade Single Mode Patchcord as an Optical Extensometer Based on Bending Loss

Power loss occured in a bent optical fiber is not desired in communication systems. Therefore, modern optical fiber is generally made with a low bending loss and, for some fibre, its refractive index profile is specially designed so that the fiber is not sensitive to the bending. For optical fibers intended as sensors, the bending loss is actually utilized for that purpose and are designed in such a way in order to be very sensitive to the bending. In this paper we describe the use of an SMF-28 optical fiber patchcord, which is commonly used in communication systems and not categorized as a bendsensitive fiber, as an extensometer (an instrument to measure the displacement or deformation of an object) by utilizing the characteristic curve of its bending loss at wavelengths of 1550 nm and 1310 nm. In our experiment, a single loop of an SMF-28 patchcord is clamped between the jaws of a vernier caliper. For the light source we use two diode lasers available in the OTDR Anritsu MT9083, and to measure the optical power we use a power meter Anritsu ML9002A. Position of the vernier caliper is then changed from 27 mm to 10 mm by 0.1 mm decrement and the value of the bending loss is calculated from the measured power at each position minus the measured power of the straight fiber. From the characteristic curve it is obtained that the bending loss is not a monotonic function but oscillatory. For displacement from 27 mm to 19 mm we used a light source with a wavelength of 1550 nm, while for displacement from 19 mm to 10 mm we use the 1310 nm wavelength, and each has a resolution of 0.3 mm. For a specific application with a limited range (i.e. from 21 to 20 mm for a wavelength of 1550 nm, and from 11.6 to 11 mm for a wavelength of 1310 nm) the obtained resolution is about 0.025 mm if the resolution of the power meter is 0.05 dB.

Intensity based sensor based on single mode optical fiber patchcords

This paper describes the use of several single mode (SM) fiber patchcords available commercially in the market for intensity based sensor by taking the benefit of bending loss phenomenon. Firtsly, the full transmission spectrum of all fiber patchcords were measured and analyzed to examine its bending properties at a series of wavelength using white light source and optical spectrum analyzer. Bending spectral at various bending diameter using single wavelength light sources were then measured for demonstration.Three good candidates for the intensity based sensor are SM600 fiber patchcord with 970 nm LED, SMF28 fiber patchcord with 1050 nm LED and 780HP fiber patchcord with 1310 nm LED which have noticeable bending sensitive area. Experiments show that the combination of the SMF28with 1050 nm LED has 30 mm measurement range which is the widest; with sensitivity 0.107 dB/mm and resolution 0.5 mm compared with combination of SM600 patchcord and LED 970 nm which has the best sensitivity (0.891 dB/mm) and resolution (0.06 mm) but smaller range measurement (10 mm). Some suitable applications for each fiber patchcord – light source pair have also been discussed.

Investigation on the use of standard single mode fiber as a displacement sensor using 1050 nm LED light source

The use of standard single mode fiber using 1050 nm LED as displacement sensor was studied by examining the bending loss of the fiber. Three standard single mode fibers: jacketed and unjacketed patchcords, 2 m long each; and a 140 m length Fujikura fiber were used in this experiment. To simulate the displacement process, a fiber loop was clamped between the jaws of a vernier caliper to form a loop. Then, one of the movable jaw was shifted gradually every 0.5 mm resulting in the change of the diameter of the fiber and also the fiber output power. The value of the bending loss was measured as the output power at each position of the vernier caliper when varied from 50 to 10 mm. Investigation of bending loss values for all the fibers resulted in measurement range of 40 mm and resolution of 0.65–1.2 mm, depended on the material coating and the physical diameter of the fiber. Furthermore, the whispering gallery modes effect was unnoticeable and the relationship between output (bending loss, dB) and input (disp...

Preliminary design of land displacement-optical fiber sensor and analysis of observation during laboratory and field test

An optical fiber optic sensor for detecting land displacement is discussed in this paper. The sensor system consists of a laser at wavelength 1.3 um, optical fiber coupler, optical fiber as sensor and light transmitting media, PIN photodiodedetector system, data logger and personal computer. Sensor was made from a curved optical fiber with diameter 35 mm, which will be changed into a heart-shape fiber if it is pulled. The heart-shape fiber sensor is the modification of the earlier displacement fiber sensor model which was in an ellipse form. Light to and from the optical fiber sensor was transmitted into a length of a multi core, single mode optical fiber cable. The scheme of the optical displacement sensor system has been described here. Characterization in the laboratory has been done by applying a series of pulling mechanism, on the heart-shape fiber sensor; which represents the land displacement process. Characterization in the field was carried out by mounting the sensor system on a scaled-down model of a land slope and artificially reproducing the landslide process using a steady-flow of artificial rainfall as the trigger. The voltage sensor output was recorded during the artificial landslide process. The displacement occurence can be indicated from the declining of the sensor signal received by the detector while the reference signal is steady. Characterization in the laboratory resulted in the performance of the optical fiber land displacement, namely, sensitivity 0.027(mV/mV)/mm, resolution 0.37 mm and measurement range 30 mm; compared with earlier optical fiber sensor performance with similar sensitivity and resolution which works only in 8 mm displacement range. Based on the experiment of landslides simulation in the field, we can define a critical condition in the real situation before landslides occurence to take any measures to prevent more casualties and losses.

Design of instrumentation for flatness measurement of railroads

Transportation safety issues are very important; one of which is related to a mode of land-based transport in particular a railroad train. This research thus develops and designs a flatness measurement system consisting of multiple sensors to determine whether railroads are flat. The method used in this study is to deploy sensors for measuring flatness on railway carriages from one railway station to another. The measurements provide field data about translational and rotational shifts of position and angle in particular locations. The magnitudes of the shifts are obtained from the Inertial Measurement Unit (IMU) integrated sensor that contains Accelerometer Sensor, Compass Magnetometer, Gyroscope, Air Pressure Sensor and GPS. LabVIEW 2013 is here used in cooperation with GUI systems equipped with a data logger for automatic data saving.

Fabrication of infrared LEDs/LDs at wavelength of 1.5 μm using LPE-grown wafer

We describe our research on the fabrication of GaInAsP/InP Light Emitting Diodes (LEDs)/Laser Diodes (LDs) at wavelength of 1.5 micrometers using wafer grown by Liquid Phase Epitaxy (LPE) system. The source materials are baked at temperature of 610 degrees C at the horizontal LPE system. The epitaxially layers are formed on InP substrate in the graphite boat with the cooling rate of 0.7 degrees C/min. The wafers are characterized using Scanning Electron Microscope (SEM), Photoluminescence (PL) and x-ray Diffraction (XRD) techniques. It is formed into LED chips by cleaving method after metalization, annealing and lapping processes. About 20-30 LED chips can be obtained from a wafer. Characterization has been conducted to examine the LED basics characteristics which showing the diode characteristics of the chips at its voltage-current curve. Furthermore, electroluminescence process is conducted by giving an instantaneous current pulse on the chip and detecting the output light using Ge detector; resulting a voltage-time curve displayed at a digital storage oscilloscope. The spectrum of the LED chip was observed by using an optical spectrum analyzer, giving peak wavelength at (lambda) approximately 1.5 micrometers with spectral width between 90-105 nm. Future works in fabrication of GaInAsP/InP LD at this wavelength is still underway starting with preliminary experiment of photolithography and etching techniques of LPE grown wafers is conducted.