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.
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.
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.
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.
An optical fiber laser with ring structure has been built. The fiber ring laser consists of an erbium doped fiber which is spliced into the two selective ports of a conventional fused fiber coupler. Argon laser at (lambda) equals 514.5 nm was used as the pump source. Pulses of 1 mW peak power and 80 microsecond(s) duration were observed at a wavelength of 1535 nm.