We experimentally demonstrated a multi-wavelength Brillouin Raman fiber laser with 20 GHz spacing utilizing a dual laser cavity that operated in the L-band wavelength region. In this laser configuration, 11 km long dispersion compensating fiber provided Brillouin gain medium. At Brillouin pump (BP) wavelength of 1580 nm, BP power of 7 dBm and Raman pump power of 1259 mW, 102 Brillouin stokes signals were produced over 14.3 nm of bandwidth. By adjusting appropriate BP wavelength within 1580–1600 nm a tuning range over 20 nm was obtained. In additional, average OSNR of 21.7, 17.8, 16.9, 15.5 and 16.9 dB are recorded for wavelength at 1580, 1585, 1590, 1595 and 1600 nm respectively.

This Letter reports a lead (II) ion sensor composed of a tapered multimode fibre (MMF) coated with chitosan. The diameter and length of the tapered fibre region is 20 µm and 1 cm, respectively. Tapered MMF is used because it is more flexible and compact compared with plastic clad silica. Chitosan is chosen as the sensing layer because it can absorb heavy metal ions due to its unique properties as polyelectrolyte and chelating agent. The refractive index of the chitosan layer changes as it absorbs lead (II) ion and this leads to an increase in the absorbance measured by the spectrophotometer. This is tested by immersing the sensor in a solution that contains lead (II) ion with different concentrations, from 0.2 to 1 ppm. The results show that the absorbance measured by the spectrophotometer increased as the concentration of the lead (II) ion increased. The sensor's average sensitivity is measured as 40.554 abs/ppm. This sensor is simpler compared with surface plasmon resonance-based lead (II) ion sensor because it does not require metal coating prior to the sensing layer coating.

In this paper, passively Q-switched fiber laser is demonstrated and the laser output energy is stabilized by using 2.4 m Erbium-doped fiber laser (EDFL) with a graphene oxide used as saturable absorber (GO-SA). According to the experimental results in the Q-switched configuration, the laser cavity emits a wavelength centered at 1,558.75 nm, and by inserting the GO-SA into EDFL cavity, hence, the laser output energy around 1.68 nJ with an FWHM pulse width of 2.3 µs at 123.5 kHz was achieved.

The effect of transversal design in Erbium-doped fiber amplifiers’ gain and noise figure performance is illustrated in this work. In this work, we investigate experimentally a single pass 980 nm pumped EDFA with partially doped Erbium core fiber (PDCF), which has the core partially doped with Erbium ions. Later, the enumerated results for PDCF are compared with a standard fully doped EDF, having similar Erbium ion doping concentration. The PDCF Amplifier gain and noise figure performance is studied against different pump power and signal power at different operating wavelengths. The noise figure indicates improvement due to reduced spontaneous emission from un-doped region of the core.

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