Design And Development Of Remotely Pumped Erbium Doped Fiber Amplifier Transmission System

Erbium Doped Fiber Amplifier (EDFA) has been deployed extensively in optical communication systems especially for a long haul transmission link. Basically, EDFA requires a local pump laser for its optical amplification. This design will encounter problem if the amplifier is located at the middle of transmission line where power supply for the pump laser is unavailable. Therefore, remotely pumped amplifier can overcome the problem by injecting the pump light from either side of the transmission ends; transmitter or receiver. This dissertation reveals a new technique of designing a repeaterless transmission system using a remotely pumped EDFA. By varying the length of transmission fiber before and after EDFA, its location can be optimized for a specific pump power. A bit error rate is used as the main performance parameter and its threshold value is set at better than 10-10. The optimized location of EDFA will lead to the maximum transmission distance where it is found that the location of EDFA is closer to the receiver side.In conclusion, the EDFA location on transmission line using remotely pumped technique gives major impact to the system’s performance

Two-photon photoluminescence induced defects on InGaN crystal and light emitting diodes

Two-photon excitation techniques used in fabricating lines defects were done on a light emitting diode chip. Simultaneous detection of a quenched wide-gap semiconductor crystal has been observed using single- and two-photon photoluminescence. It was found at the quenched area, single-photon excitation gives photoluminescence read-out compared to two-photon excitation which no photoluminescence detected at the bandgap wavelength. This is due to the excitation states which the transition of electron for two-photon excitation to occur have been demolished by the annealing of the sample which involved two-photon quenching process. The dependency of excitation power with respective photoluminescence is elaborated to confirmed the single- and two-photon excitation photoluminescence methods

Performance configuration of Raman-EDFA hybrid optical amplifier for WDM applications

A hybrid configuration of Raman amplifier and erbium-doped fiber amplifier (EDFA) is proposed to obtain a better performance in term of gain, noise figure and flat gain. It is based on the optimum parameter configuration of a singly-based Raman amplifier and EDFA. The best parameter for both amplification has been analyze in terms of its input signal power, pump power and their fiber length whereas the best erbium ion density has also been analyze in EDFA setup. All the parameters are varied to some values to get the optimum result. The simulation is done by using Optisystem 14.0 software. The hybrid amplifier consists of Raman amplifier with multi-pump power set up and bidirectional pump power of EDFA with the pump wavelength of 980 nm is designed and simulated in order to obtain higher gain and lower noise figure. From the simulation of the hybrid configuration, the optimum output has been achieved. The hybrid configurations exhibit the average gain of 46 dB and average noise figure of 3 dB. The flat gain obtained is between 1530 nm to 1600 nm which include C-Band and L-Band frequency with the gain bandwidth of 70 nm.

Frequency modulation optimization of nonlinear optical Z-scan by high repetition rate femtosecond laser

Nonlinear optical properties of 2- (2-hydroxyethyl)-6-(morpholin-4-yl) -1H-benzo[de]isoquinoline- 1,3(2H)- dione pigment material is investigated with frequency modulation of 250 MHz femtosecond high repetition rate (HRR) laser by an optical chopper. Thermal lensing formation on the material due to thermal build up from HRR laser leads to measurement ambiguity of nonlinear refractive index (NLRI) and two-photon absorption cross section (TPACS). Optimized optical chopper frequency range of 50% duty cycle modulated laser beam effectively reduces laser contact time on the material and resulted in improved NLRI and TPACS of -8.23 × 10-18 m2/W and 2.96 GM respectively

Frequency and duty cycle modulation optimization in minimizing thermal accumulation effect in Z-scan measurement with high-repetition-rate laser

In this study, we demonstrate the optimization of the chopper frequency and duty cycle in a Z-scan measurement with a 250 MHz high-repetition-rate (HRR) femtosecond laser to minimize the thermal lensing effect due to cumulative heating of the sample. The result shows that such minimization can be achieved by keeping the modulated exposure time on the sample shorter than the thermal diffusivity decay time tc. The minimum chopper frequency fmin is predicted by relating the duty cycle factor F with tc, while maintaining stable peak and valley transmittances, i.e., ΔTp and ΔTv, respectively. Furthermore, a lower fmin is obtained by taking a stable range of the peak–valley difference ΔTpv into consideration. The optimization allows for the low operational modulation frequency of Z-scan measurement with reduced thermal influence, thus enabling simple management of the thermal lensing effect

Dual-wavelength thulium ytterbium Co-doped fiber laser

We report on the generation of dual-wavelength fiber laser peaking at 1990.64 and 1998.92 nm with a simple ring cavity setup. The lasers are demonstrated using a fabricated silica-based nanoengineered octagonal shaped double-clad Thulium-Ytterbium co-doped fiber (TYDF) as a gain medium in a simple all-fiber ring configuration. By using 980 nm multimode laser, a stable dual-wavelength laser is generated at a threshold pump power of 1500 mW due to the non-polarization rotation (NPR) effect occurred in the cavity. The effect has been self-controlled by a suppression of mode competition in the gain medium. The result shows that the slope efficiency of the generated dual–wavelength laser is measured to be 27.23%. This dual-wavelength TYDF laser operated steadily at room temperature with a 34 dB optical signal-to-noise rati

PASSIVELY Q-SWITCHED YTTERBIUM-DOPED FIBER LASER EMPLOYING SAMARIUM OXIDE AS SATURABLE ABSORBER

The rapid developments in transition metal dichalcogenide materials as a saturable absorber (SAs) have been demonstrated to be an effective method for generating Q-switched fiber laser. This work, reports on the generation of Q-switched fiber laser in the 1-micron region using samarium oxide (Sm2O3) saturable absorber (SA). The Sm2O3 thin film SA was fabricated in- The rapid developments in transition metal dichalcogenide materials as saturable absorbers (SAs) have been reported to be efficient materials for generating Q?switched fiber lasers. In this paper, we report on the use of samarium oxide (Sm2O3) saturable absorber (SA) for 1-micron Q-switched fiber laser generation. The Sm2O3 thin film SA was constructed in-house through which the Sm2O3 powder was mixed and stirred in polyvinyl alcohol (PVA) solution. It was then integrated into the ytterbium-doped fiber laser (YDFL) ring cavity, hence producing a sequence of Q-switched pulsed lasers at 1062.49 nm wavelength. The stable pulse train appeared from 69.97 to 111.1 kHz between the applied pump power of 57 mW to 96 mW. The signal-to-noise ratio (SNR) of 38.56 dB was recorded at the 57 mW pump power, whereas the pulse energy raised until 15.21 nJ at 96 mW. These results showed that the Sm2O3 could be a favourable SA material to iniatiate Q-switched ytterbium-doped pulsed fiber laser. ABSTRAK: Perkembangan pesat dalam bahan logam peralihan dichalcogenide sebagai bahan penyerap boleh larut (SAs) telah dilaporkan sebagai kaedah yang berkesan bagi menjana laser fiber Q-switched. Kajian ini menggunakan samarium oksida (Sm2O3) saturable absorber (SA) bagi menjana laser gentian Q-switched 1-Micron. Filem nipis Sm2O3 SA telah dihasilkan melalui campuran serbuk Sm2O3 ke dalam cecair polivinil alkohol (PVA) dalam persekitaran makmal. Kemudian, ia diintegrasi ke dalam rongga gelang laser gentian dop-ytterbium (YDFL), lalu menghasilkan denyut laser Q-switched stabil pada jarak gelombang 1062.49 nm. Denyutan stabil muncul dari 69.97 kepada 111.1 kHz pada kuasa pam yang dikenakan antara 57 mW hingga 96 mW. Nisbah isyarat-hinggar (SNR) pada 38.56 dB telah direkodkan pada pam kuasa 57 mW, sementara denyut tenaga ditingkatkan kepada 15.21 nJ pada 96 mW. Keputusan menunjukkan Sm2O3 merupakan bahan SA penggalak yang memuaskan bagi menjana denyut laser gentian dop-ytterbium Q-switched. house. It was integrated into the ytterbium-doped fiber laser (YDFL) ring cavity, hence producing a stable passively Q-switched laser operating at 1062.49 nm wavelength. Stable pulse train appeared from 69.97 to 111.1 kHz at the tunable pump power of 57 mW to 96 mW. The pulse energy of up to 15.21 nJ and signal-to-noise ratio (SNR) of 38.56 dB for the fundamental frequency were recorded. The results showed that the Sm2O3 could be a favourable SA material for the broadband generation of Q-switched fiber laser

Z-scan technique with high repetition rate femtosecond laser for nonlinear optical properties measurement

Nonlinear optical properties are crucial in determining the behavior of the optical material under the intense laser beam. Z-scan method is a simple technique to measure nonlinear refraction and absorption with high degree of sensitivity and noncomplex arrangement setup. Ultrafast laser technology benefits the Z-scan method by providing high nonlinearity condition within the material. Nevertheless, most of today’s ultrafast lasers are designed with high repetition rate (HRR) pulse trains which is known able to trigger thermal lensing effect. The lensing formation in Z-scan measurement corrupts the pure nonlinear response thus exhibits invalid results. Thermal lensing effect by the HRR laser is originated by the accumulated heat across the pulse trains due to the significantly long thermal diffusion time of the material in comparison to the very short HRR pulse separation. Optical chopper deployment in Z-scan measurement limits the material time exposure to the HRR beam and eliminates the lensing effect with the optimized chopper frequency. However, the optimization comes with a fixed chopper duty cycle, typically equal opening and blanking period. Therefore, applying duty cycle variation on top of the chopper frequency would reveal a new working range for the Z-scan to obtain accurate measurements without the thermal lensing influence. This research reports the Z-scan measurement with 780 nm HRR femtosecond beam on the nonlinear material AC-39. The experiment is performed with the adoption of the chopper frequency and duty cycle variation to minimize the thermal lensing effect by the precisely control the exposure time on AC-39. The modulated HRR beam Z-scan is carried out over the modulation frequency and duty cycle variation by evaluating the change of the peak and valley transmittance. For a 50% fixed duty cycle, 500 Hz of optimized minimum chopper frequency is achieved. The minimum chopper frequency is reduced further by adopting 10 and 25% duty cycle. It is deduced that this optimization is obtained by keeping the HRR beam time exposure on AC-39 material well below its thermal diffusivity time, thus seizes the thermal lensing build up formation before the next duty cycle. The minimum chopper frequency is correctly predicted by associating the chopper duty cycle factor, F with the material thermal diffusivity time, tc. Additional frequency optimization is achieved by considering the stable peak-valley transmittance difference over the frequency variations. The technique of finding the optimized minimum chopper frequency leads to the thermal diffusivity determination of the sample material for the unknown thermal diffusivity time. The optimization opens up for a potential of low operational frequency and offers a simple and straightforward solution and implementation in Z-scan technique of nonlinear optical properties measurement with high repetition rate femtosecond laser

Preliminary analysis of dimming property for visible light communication

Visible light communication (VLC) is an emerging and promising new technology in optical wireless communication (OWC). However, dimming affects the performance of the visible light communication system. In visible light communication (VLC) system, illumination and communication both are provided simultaneously using light-emitting diode (LED). The dimming control applicable and required for the lighting system. There are different modulation techniques for dimming control in visible light communication. In this paper, only the NRZ-OOK modulation method is investigated for different dimming range, transmission distance, beam divergence angle and bit rate. Optisystem Software is a tool that analyze the performance of the system. The result shows that by increasing the link from 10 m to 63 m, the obtained BER is 6.16656×10-9, Q factor is 5.6919 and 400kb/s data speed. However, the achieved data rate is still unsatisfactory for the VLC system. We increased the data rate from 400kb/s to 2Mb/s, but the distance between transmitter and receiver decreased to 3m by maintaining BER of 1.33827×10-9. It means that high-speed data transmission by using NRZ-OOK is for short distance only. The scope of this research excluded the following parameters which are shadowing, mobility, multipath interference and intersymbol interference for multicarrier modulation. These are the related research topic which is for future work