M. Z. Muhammad

Micro-Ball Lensed Fiber-Based Glucose Sensor

The compact micro-ball lens structure fabricated at the cleaved tip of a microfiber coupler (MFC) is proposed and demonstrated for sensing various glucose concentrations in deionized water. The MFC was made by fusing and tapering two optical fibers using a flame brushing technique. It was then cleaved at the center of the minimum waist region to form a ball lens at the tip by an arcing technique using a fusion splicing machine. The proposed glucose sensor uses the micro-ball lensed fiber as a probe and a mirror as a target. The working mechanism of this device is based on the observed reduction in the peak power of the sensor wavelength spectrum as the concentration of glucose is increased. For a concentration change from 0 to 12 volume%, the ouput intensity of the sensor decreases linearly from -57.4 to -60.5 dBm with a sensitivity of 0.26 dB/% and a linearity of more than 99%.

Compact Dual-Wavelength Laser Generation Using Highly Concentrated Erbium-Doped Fiber Loop Attached to Microfiber Coupler

A compact and low noise dual-wavelength fiber laser is demonstrated using a 70-cm-long Erbium-doped fiber loop attached to a microfiber coupler. The coupler functions to inject a 980-nm pump light as well as to tap out the output. At the maximum pump power of 8.4 mW, dual-wavelength laser is obtained at 1537.7 and 1551.4 nm with peak powers of 20.5 and 20.9 dBm, respectively. Both laser outputs are stable with a signal to noise ratio of more than 35 dB at room temperature. Both 1537.7 and 1551.4 nm lasers start to lase at threshold pump power as small as 2.5 mW with efficiencies of 0.14% and 0.10%, respectively.

Fabrication and Characterization of a 2×2 Microfiber Knot Resonator Coupler

A 2 × 2 microfiber knot resonator (MKR) coupler is demonstrated. The hybrid device is obtained by forming a knot within the coupling region of a microfiber coupler with a 50:50 splitting ratio. The microfiber coupler is successfully fabricated by laterally fusing and tapering two optical fibers using a flame-brushing technique. The coupler has an overlapping length of 40 mm with a uniform waist of around 5 μm. With an MKR structure, the coupler produces a resonant response at both output ports. The free spectral range of the output spectrum from both ports is obtained at 0.2 nm at a knot diameter of 260 μm. The resonance extinction ratio of the device varies from 2 to 6 dB while the calculated Q factor and finesse are ~25646 and 3.3, respectively, at both output ports.

Tapered Fiber Coated with Hydroxyethyl Cellulose/Polyvinylidene Fluoride Composite for Relative Humidity Sensor

A simple relative humidity (RH) sensor is demonstrated using a tapered fiber coated with hydroxyethyl cellulose/polyvinylidene fluoride (HEC/PVDF) composite as a probe. This coating acts as an inner cladding whose refractive index decreases with the rise in humidity and thus allows more light to be transmitted in humid state. A difference of up to 0.89 dB of the transmitted optical power is observed when RH changes from 50% to 80% in case of the silica fiber probe. The proposed sensor has a sensitivity of about 0.0228 dB/%RH with a slope linearity of more than 99.91%. In case of the plastic optical fiber (POF) probe, the output voltage of the sensor increases linearly with a sensitivity of 0.0231 mV/%RH and a linearity of more than 99.65% as the relative humidity increases from 55% to 80%.

Erbium-doped fibre ring laser based on microfibre coupler

A compact erbium- doped fibre (EDF) laser is demonstrated which uses a microfibre coupler and a highly concentrated EDF loop. The coupler functions to inject the pump light and tap out the output. The EDF laser operates at 1526.3 nm, with a signal-to-noise ratio of about 26 dB. The maximum output power 20 µW is obtained at the pump power 18.6mW. We have obtained the slope efficiencies of the laser 0.12, 0.06, 0.04 and 0.02% at the EDF lengths fixed at 90, 78, 66 and 51 cm, respectively. The lowest lasing-pump power threshold is achieved at 3.8 mW