Pump distribution effect in dual-wavelength Raman-erbium random distributed feedback fiber laser.

This work demonstrates a simple dual-wavelength random distributed feedback fiber laser via excitation of the Raman-erbium hybrid gain by a single pump source. Lasing wavelengths at 1568 nm and 1595 nm with 48.48 dBm maximum OSNR were generated without the need for physical reflectors. Enhancements were performed using pump power distribution and a seeded feedback to reduce the peak disparity to only 0.16 dB. The long cavity hybrid random laser with its balanced and broadly spaced dual-wavelength output offers immense potential for long distance dual laser applications.

Dual-wavelength, mode-locked erbium-doped fiber laser employing a graphene/polymethyl-methacrylate saturable absorber.

Mode-locked fiber laser incorporating a saturable absorber is an attractive configuration due to its stability and simple structure. In this work, we demonstrate a dual-wavelength passively mode-locked erbium-doped fiber laser employing a graphene/polymethyl-methacrylate saturable absorber. A laser resonator is developed based on dual cavity architecture with unidirectional signal oscillation, which is connected by a fiber branch sharing a common gain medium and saturable absorber. Dual wavelength mode-locked fiber lasers are observed at approximately 1530 and 1560 nm with 22.6 mW pump power threshold. Soliton pulse circulates in the laser cavity with pulse duration of 900 and 940 fs at shorter and longer wavelengths, respectively. This work presents a viable option in developing a low threshold mode-locked laser source with closely spaced dual wavelength femtosecond pulses in the C-band wavelength region.

Wavelength-tunable single longitudinal mode fiber optical parametric oscillator.

We demonstrate a ring cavity single longitudinal mode fiber optical parametric oscillator using a passive sub-ring cavity and an unpumped erbium doped fiber configured with an external fiber mirror for single mode selection. The unpumped erbium doped fiber uses its saturable absorption characteristic to generate a self-induced narrowband filter when two counter-propagating waves interfere inside the fiber. A single longitudinal mode laser is obtained with a linewidth of 17.35 kHz at a pump power of 31.2 dBm. A 3.8 nm tuning range from 1536.5 nm to 1540.3 nm is achieved with a signal-to-noise ratio of about 60 dB. The power stability of the single longitudinal mode laser is 2.07 dB over a period of 30 minutes.

Effects of Raman pump power distribution on output spectrum in a multi-wavelength BRFL.

This paper aims to investigate changes in multi-wavelength Brillouin-Raman fiber laser (MBRFL) spectra characteristics that are influenced by variation of Raman pump power distribution along the two fiber-entry points. This is carried out by incorporating a Raman pump source with a set of couplers with various ratios. In this arrangement, the optimization of pumping ratio is properly carried out to achieve high number of lasing lines with 20 GHz spacing which yield the highest peak power discrepancy between odd- and even-order lasing lines and an excellent Stokes optical signal-to-noise ratio (S-OSNR). Employment of 50/50 coupler offers 212 flat amplitude channels with an average 27.5 dB S-OSNR and -10 dBm Stokes peak power when the Brillouin pump wavelength is set at 1543 nm. Achievements such flat and wide bandwidth MBRFL spectrum with 20 GHz spacing and excellent S-OSNR utilizing just a single pump source is significant in terms of simplicity and flexibility.

Effects of Raman pump power distribution on output spectrum in a multi-wavelength BRFL: publisher's note.

This publisher's note amends the author list and Acknowledgments of a recent publication [Opt. Express23, 25570 (2015)].

Room temperature ammonia sensing using tapered multimode fiber coated with polyaniline nanofibers.

We demonstrate an ammonia sensor composed of a tapered multimode fiber coated with polyaniline nanofibers that operates at room temperature (26°C). The optical properties of the polyaniline layer changes when it is exposed to ammonia, leading to a change in the absorption of evanescent field. The fiber sensor was tested by exposing it to ammonia at different concentrations and the absorbance is measured using a spectrophotometer system. Measured response and recovery times are about 2.27 minutes and 9.73 minutes, respectively. The sensor sensitivity can be controlled by adjusting the tapered fiber diameter and the highest sensitivity is achieved when the diameter is reduced to 20 µm.

Extended nonlinear parametric process in anomalously pumped linear cavity oscillator.

We demonstrate a linear cavity fiber optical parametric oscillator with extended pump-signal separation of 14.3 THz (116 nm). The signal laser is provided by a pair of 1675nm fiber Bragg gratings and a tunable idler from 1456.12 nm to 1462.48 nm is generated by detuning the pump wavelength in the anomalous dispersion regime of a highly nonlinear fiber. At such large pump-signal separation, we are still able to record a parametric conversion efficiency of more than -35 dB and idler optical signal-to-noise-ratio of 50 dB on average. The stability of the lasing signal and idler is examined and result shows both signal and idler peak power fluctuation is less than 1 dB over a period of 30 minutes.

Single mode tapered fiber-optic interferometer based refractive index sensor and its application to protein sensing.

We demonstrate refractive index sensors based on single mode tapered fiber and its application as a biosensor. We utilize this tapered fiber optic biosensor, operating at 1550 nm, for the detection of protein (gelatin) concentration in water. The sensor is based on the spectroscopy of mode coupling based on core modes-fiber cladding modes excited by the fundamental core mode of an optical fiber when it transitions into tapered regions from untapered regions. The changes are determined from the wavelength shift of the transmission spectrum. The proposed fiber sensor has sensitivity of refractive index around 1500 nm/RIU and for protein concentration detection, its highest sensitivity is 2.42141 nm/%W/V.

Analytical analysis of second-order Stokes wave in Brillouin ring fiber laser.

This paper details a theoretical modeling of Brillouin ring fiber laser which incorporates the interaction between multiple Brillouin Stokes signals. The ring cavity was pumped at several Brillouin pump (BP) powers and the output was measured through an optical coupler with various coupling ratios. The first-order Brillouin Stokes signal was saturated with the presence of the second-order Stokes signal in the cavity as a result of energy transfer between them. The outcome of the study found that the optimum point for the first-order Stokes wave performance is at laser power reduction of 10%. Resultantly, at the optimum output coupling ratio of 90%, the BFL was able to produce 19.2 mW output power at BP power and Brillouin threshold power of 60 and 21.3 mW respectively. The findings also exhibited the feasibility of the theoretical models application to ring-type Brillouin fiber laser of various design parameters.

Spectral variations of the output spectrum in a random distributed feedback Raman fiber laser.

We report an ultra-long Raman laser that implemented a variable pumping scheme in backward and forward configurations. Rayleigh backscattering effects were realized in the 51 km fiber length that functioned as a virtual mirror at one fiber end. With the employment of a fiber Bragg grating that has a peak reflection wavelength at 1553.3 nm, spectral broadening effects were observed. These occurred as the pump power level was diverted more to the forward direction. Owing to this fact, a maximum width of 0.9 nm was measured at 100% forward pumping. The obtained results show that the efficient exploitation of four-wave mixing interactions as well as strong Rayleigh backscattering are beneficial to influence the lasing performances. Both of these nonlinear responses can be adjusted by varying pumping distributions along the fiber longitudinal dimension.

Results of group-circumcision of Muslim boys in Malaysia with a new type of disposable clamp.

This study evaluates the safety and results of surgery usingTaraKlamp Circumcision Device during a group circumcision. Atotal of 64 circumcisions of Muslim boys were performed by Medical Assistants supervised by Medical Doctors in a hall in Kuala Lumpur, Malaysia. A new type disposable clamp was used, which was removed 4 days after the operation. No major complications occurred and the boys experienced in general mild pain postoperatively. Mostly good cosmetic results were obtained and 90% of the parents would recommend this new clamp to others. Group circumcisions withTaraKlamp Circumcision Device (Kuala Lumpur, Malaysia) are safe, although proper patient selection and adequate training in using the device are mandatory.