An Efficient and Low Noise L-band Erbium-Doped Fiber Amplifier

The use of the long-wavelength-band (Lband) is attractive for both increasing the capacity of wavelength division multiplexing (WDM) systems and has been used in WDM transmission experiments at over 1 Tb/s. Recently, a gain bandwidth of about 80nm has been achieved by integrating the L-band EDFA in parallel with conventional band (Cband) EDFA [1]. Moreover, the L-band EDFAs will make it possible to construct an effective WDM systems employing dispersion-shifted fiber (DSF) without the degradation caused by four-wave-mixing (FWM) [2]. The L-band erbium-doped fiber amplifier (EDFA) is studied because it can be constructed by silica-based erbium-doped fiber (EDF) and has a low linearity for WDM signals. However, L-band EDFAs have a low power conversion efficiency (PCE) compared to a C-band

Passive Q-switched and Mode-locked Fiber Lasers Using Carbon-based Saturable Absorbers

This chapter aims to familiarize readers with general knowledge of passive Q-switched and mode-locked fiber lasers. It emphasizes on carbon-based saturable absorbers, namely graphene and carbon nanotubes (CNTs); their unique electronic band structures and optical characteristics. The methods of incorporating these carbon-based saturable absorbers into fiber laser cavity will also be discussed. Lastly, several examples of experiments where carbon-based saturable absorbers were used in generating passive Q-switched and mode-locked fiber lasers are demonstrated

Zinc oxide nanoparticles based passive saturable absorber for pulse generation in fiber laser

A stable passive Q-switched pulsed generation in Erbium doped fiber laser by Zinc Oxide nanoparticles embedded in polyvinyl alcohol (ZnONP-PVA)-based saturable absorber is demonstrated in this paper. The surface morphology and thickness profile of the fabricated film were observed using FESEM and 3D measuring laser microscope with the measured thickness of 12 μm. Meanwhile the its optical properties is characterized using Raman spectroscopy. The developed ZnONP-PVA film, has modulation depth of 7.8% and intensity saturation of 88.97 MW/cm2. The threshold input pump power to generate Q-switched pulse is at 45.4 mW and can be tuned until 92.4 mW before the pulse diminished. The operating wavelength of generated pulse is at 1535 nm with 3 dB bandwidth approximately of 2 nm with exclusion of parasitic continuous wave lasing. As the input pump power was tuned from threshold to maximum value, the recorded pulse train of repetition rate is tunable from 73.53 kHz to 103.10 kHz while the pulse width decreases from 6.8 μs to 4.8 μs. The calculated maximum output power and pulse energy at maximum input pump power was 5.14 mW and 49.85 nJ, respectively. The measured signal to noise ratio was 56 dB indicated that the generated pulse by ZnO NP based passive saturable absorber was stable

50 cm of Zirconia, Bismuth and Silica Erbium-doped Fibers for Double-pass Amplification with a Broadband Mirror

Erbium-doped fiber amplifiers (EDFAs) have saturated the technological market but are still widely used in high-speed and long-distance communication systems. To overcome EDFA saturation and limitations, its erbium-doped fiber is co-doped with other materials such as zirconia and bismuth. This article demonstrates and compares the performance using three different fibers as the gain medium for zirconia-erbium-doped fibers (Zr-EDF), bismuth-erbium-doped fibers (Bi-EDF), and commercial silicaerbium-doped fibers (Si- EDF). The optical amplifier was configured with a double-pass amplification system, with a broadband mirror at the end of its configuration to allow double-pass operation in the system. The important parameters in amplifiers such as optical properties, optical amplification and noise values were also examined and discussed. All three fibers were 0.5 m long and entered with different input signals: 30 dBm for low input and 10 dBm for high input. Zr-EDF turned out to be the most relevant optical amplifier as it had the highest optical gain, longest transmission distance, highest average flatness gain with minimal jitter, and relevant noise figures suitable for the latest communication technology

Graphene Nanoplatelets (GnP)-PVA Based Passive Saturable Absorber

A passive Q-switched pulsed laser at 1.5 m region incorporating graphene nanoplatelets (GnPs) embedded in Polyvinyl Alcohol (PVA) is demonstrated. A surfactant is used to aid the dispersion of the GnPs before it is mixed with PVA to develop a GnPs-PVA film based SA. The SA is integrated into the laser cavity by attaching a cut of the GnPs-PVA film in between two fiber ferrule of the laser ring cavity.The proposed GnPs-PVA film based passive Q–switched laser was able to operate as the input pump power was increased from 39 mW up to a maximum of 148 mW before diminishing. The laser obtained operated with a central wavelength of 1530.76 nm. Repetition rates were obtained at 33 kHz to 91.5 kHz, throughout the tunable input pump power with the shortest pulse width of 2.42 s. Maximum attainable peak power and pulse energy of 1.2 mW and 5.9 nJ, respectively, was recorded, accompanied by a signal to noise ratio (SNR) of 28 dB

Tapered fiber coated with hydroxyethyl cellulose/polyvinylidene fluoride composite for relative humidity sensor

A new evanescent wave based sensor is proposed and demonstrated using a silica fiber interferometer coated with Hydroxyethyl Cellulose/Polyvinylidene Fluoride (HEC/PVDF) composite. The performance of the sensor is investigated for two different types of interferometer structure: inline Mach Zehnder Interferometer (MZI) with dumbell structure and non-adiabatic etched fiber. The measurement is based on interferometric technique where the transmission spectrum of the reflected light is investigated for changes in relative humidity. For instance, the resonant dip wavelength for MZI dumbbell shape increases from 1555.76 to 1556.34 nm as the RH increases from 10 to 80. While, for etched SMF the resonant dip wavelength increases from 1554.58 to 1554.85 nm as the RH increases from 10 to 80. Both sensors demonstrated a linear shift especially within a range from 20 to 45. It is found that the MZI-based sensor has a sensitivity of 0.0123 nm/ with a linearity of 99.88 and limit of detection of 0.44. On the other hand, the etched SMF structure also shows change in the resonant wavelength with the increase in RH. The tapered fiber based sensor has a sensitivity of 0.0074 nm/ with linearity of 98.85 and limit of detection of 0.65. The lower limit of detection for dumbbell structure shows that the system is more efficient than etched SMF structure. The proposed sensor has a high potential for RH measurement as it has easy to fabricate, low fabrication cost, and compact size. (C) 2015 Elsevier B.V. All rights reserved

Demotivation Factors in Using English as Daily Communication in EFL School: Case Study of EFL Learners

This study aimed to describe the causes of students' demotivation in using English for daily communication and find its solutions. The present researcher used the descriptive qualitative method. It was conducted on EFL Learners. There were 15 students to be participants in this study. The data were collected by observing, interviewing, and giving questionnaires to participants about English usage in their Islamic boarding schools. The participants' answers and the video of their daily communication were analyzed by interpreting the handy camera and checking the result of interpretation to the result of questioner and interview. Second, the present researcher compared the result of the handy camera, questioner, and interview to the existing theory to determine the causes of students' demotivation in using English as daily communication and its solution. The result analysis showed that the cause of students' demotivation is their lack of ability to use English, especially in mastering vocabulary and its pronunciation. Other factors were learning contents and materials, teachers, and failure experience. In addition, they prefer to use Arabic because Arabic has been rooted as daily communication in that Islamic boarding school. In comparison, the solution for that problem is that the teachers should pay considerable attention to the students' English ability, especially mastering and pronouncing vocabulary. Also, the teachers are suggested to pay more attention to teaching methods and their behavior to increase students' motivation and interest in second language learning. In addition, the teachers should explicitly make a regulation to divide a period for the student to speak English and Arabic

Graphene slurry based passive Q-switcher in erbium doped fiber laser

In this work, a Graphene slurry based passive Q-switcher fabricated from Graphene-Polylactic acid (PLA) filament which is used for 3D printing. To produce the Graphene slurry, the diameter of the filament was reduced and Tetrahydrofuran (THF) was used to dissolve the PLA. The Graphene-THF suspension was drop cast to the end of a fiber ferrule and the THF then evaporated to develop Graphene slurry based SA which is integrated in fiber laser cavity. At threshold input pump power of 30.45 mW, a Q-switched Erbium-doped fiber laser (EDFL) can be observed with the wavelength centered at 1531.01 nm and this remained stable up to a pump power of 179.5 mW. As the pump power was increased gradually, an increase in the repetition rates was recorded from 42 kHz to 125 kHz, while the pulse width was reduced to 2.58 μs from 6.74 μs. The Q-switched laser yielded a maximum pulse energy and peak power of 11.68 nJ and 4.16 mW, respectively. The proposed Graphene slurry based saturable absorber also produced a signal-to-noise ratio of 44 dB indicating a stable Q-switched pulsed laser