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A Partial Double-Pass S-Band Erbium-Doped Fibre Amplifier

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Chinese Physics Letters 2005年第12期22卷 3080-3082页

作者： Sulaiman Wadi Harun Nor Kamilah Saat harith ahmad Faculty of Engineering Multimedia University Jalan Multimedia 63100 Cyberjaya Selangor Malaysia Photonics Laboratory Department of Physics University of Malaya 50603 Kuala Lumpur Malaysia

An efficient and low noise short wavelength band erbium-doped fibre amplifier （S-band EDFA） is proposed and demonstrated using double-pass configuration. This amplifier provides a gain of 1500 nm signal as high as 26.9 dB, which is 9.6 dB higher than the two-stage single-pass amplifier. The corresponding noise figure obtained is 7.5 dB, which is of the same level as in the single-pass amplifier and more than 2 dB lower than the previously reported double-pass amplifier [IEIOE Electron. Express 2 （2005） 182]. The gain enhancement is due to the double pass-propagation of the test signal in the second stage, which increases the effective erbium-doped fibre （EDF） length. The low noise is attributed to the optical circulator between EDFs, which prevents the backward amplified spontaneous emission from propagating into the input part of the amplifier. The proposed amplifier is expected to play an important role in the development of a practical S-band EDFA.

关键词： Erbium doped fiber amplifiers

Graphene Oxide Functionalized Optical Planar Waveguide for Water Content Measurement in Alcohol

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Photonic Sensors 2020年第3期10卷 215-222页

作者： Wenghong LIM Yuenkiat YAP Choonkong LAI Wuyi CHONG harith ahmad Photonics Research Centre University of MalayaKuala Lumpur 50603Malaysia Heriot-Watt University Malaysia Putrajaya 62200Malaysia Department of Physics Faculty of ScienceUniversity of MalayaKuala Lumpur 50603Malaysia

An abrupt change in optical transmission characteristic of a graphene oxide(GO)coated optical planar waveguide was *** observation was based on the peculiar characteristics of the graphene oxide film,namely its high transverse-electric polarized light propagation loss,highly selective permeability of water,and change in optical propagation characteristic in the presence of *** as-fabricated GO-coated optical waveguide showed a large polarization dependent loss of~32 dB in the C-band optical fiber communication window(1550 nm).The response of the proposed sensor was first tested by using *** a drop of water was applied onto the GO coating,the large polarization dependent loss was fully suppressed almost *** effect was reversible as the polarization dependent loss was restored after complete water evaporation from the GO ***-optical measurement of water content in alcohol was then demonstrated by using the GO-coated optical *** analyzing the drying profile of the water-alcohol mixture,water content in the range of 0.2 volume%-100 volume%could be *** measurements were carried out by using solution volume of 1.0μL *** all-optical sensing nature of the proposed sensor has potential applications in in-situ monitoring of water content in alcohol.

关键词： Graphene oxide water content alcohol solution optical waveguide

Strain Sensor Based on Embedded Fiber Bragg Grating in Thermoplastic Polyurethane Using the 3D Printing Technology for Improved Sensitivity

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Photonic Sensors 2022年第3期12卷 68-78页

作者： harith ahmad Mohamad Ashraff ALIAS Mohammad Faizal ISMAIL Nor Najwa ISMAIL Muhammad Khairol Annuar ZAINI Kok Sing LIM Gilberto BRAMBILLA Kenneth T.V.GRATTAN B.MAzizur RAHMAN Photonics Research Centre University of MalayaKuala Lumpur 50603Malaysia Department of Physics Faculty of ScienceUniversity of MalayaKuala Lumpur 50603Malaysia Optoelectronics Research Centre University of SouthamptonSouthampton SO171BJUK School of Mathematics Computer Science and EngineeringCity University of LondonLondon EC1V 0HBUK

A new and easy-to-fabricate strain sensor has been developed,based on fiber Bragg grating(FBG)technology embedded into a thermoplastic polyurethane filament using a 3-dimensional(3D)*** advantage of the flexibility and elastic properties of the thermoplastic polyurethane material,the embedding of the FBG provides durable protection with enhanced flexibility and sensitivity,as compared to the use of a bare *** of an evaluation of its performance have shown that the FBG sensors embedded in this way can be applied effectively in the measurement of strain,with an average wavelength responsivity of 0.0135 nm/cm of displacement for tensile strain and -0.0142 nm/cm for compressive strain,both showing a linearity value of up to 99%.Furthermore,such an embedded FBG-based strain sensor has a sensitivity of~1.74 times greater than that of a bare FBG used for strain measurement and is well protected and suitable for in-the-field *** is also observed that the thermoplastic polyurethane based(TPU-based)FBG strain sensor carries a sensitivity value of~2.05 times higher than that of the polylactic acid based(PLA-based)FBG strain sensor proving that TPU material can be made as the material of choice as a“sensing”pad for the FBG.

关键词： Fiber-optic sensors fiber Bragg grating 3D printing technology multiple-point strain measurement

Generation of multi-wavelength erbium-doped fiber laser by using MoSe2 thin film as nonlinear medium and stabilizer

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Chinese Optics Letters 2016年第4期14卷 46-49页

作者： Zian Cheak Tiu harith ahmad Arman Zarei Sulaiman Wadi Harun Photonics Research Center University of Malaya Kuala Lumpur 50603 Malaysia Department of Electrical Engineering Faculty of Engineering University of Malaya Kuala Lumpur 50603 Malaysia

We experimentally demonstrate the application of MoSe2 thin film as a nonlinear medium and stabilizer to generate a multi-wavelength erbium-doped fiber laser. The cooperation of a photonic crystal fiber and a polari- zation-dependent isolator induces unstable multi-wavelength oscillations based on the nonlinear polarization rotation effect. A MoSe2 thin film is further incorporated into the cavity to achieve a stable multi-wavelength. The laser generates 7 lasings with a constant spacing of 0.47 nm at a pump power of 250 roW. The nmlti- wavelength erbium-doped fiber laser is stable with power fluctuations of less than 5 dB over 30 min.

关键词： nm Generation of multi-wavelength erbium-doped fiber laser by using MoSe2 thin film as nonlinear medium and stabilizer PCF EDF

Switchable Q-switched and mode-locked erbium-doped fiber laser operating in the L-band region

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Chinese Optics Letters 2013年第7期11卷 76-78页

作者： Sin Jin Tan Sulaiman Wadi Harun Hamzah Arof harith ahmad Department of Electrical Engineering Faculty of Engineering University of Malaya Photonics Research Centre University of Malaya

We demonstrate a switchable Q-switched and mode-locked erbium-doped fiber laser （EDFL） operating in the L-band region using the nonlinear polarization rotation effect. The switching operation is achieved by controlling intensity-dependent loss using a polarization controller. In Q-switching mode, the EDFL produces a pulse train with a repetition rate of 21.1 kHz, pulse width of 7.7 #s, and pulse energy of 13.6 nJ. The EDFL also generates a multi-wavelength comb with a very narrow and constant wavelength spacing of 0.045 nm and optical signal-to-noise ratio of at least l0 dB. During mode locking, the EDFL produces stretched pulses with 3-dB bandwidth of 26.2 nm, pulse width of 350 fs, repetition rate of 2.38 MHz, and pulse energy of 48.56 pJ.

关键词： mode rate EDF

Generation of Q-Switched Mode-Locked Erbium-Doped Fiber Laser Operating in Dark Regime

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Chinese Physics Letters 2016年第3期33卷 32-35页

作者： Zian Cheak Tiu Arman Zarei harith ahmad Sulaiman Wadi Harun Photonics Research Center University of Malaya Department of Electrical Engineering Faculty of EngineeringUniversity of Malaya

We demonstrate a stable Q-switched mode-locked erbium-doped fiber laser （EDFL） operating in dark regime based on the nonlinear polarization rotation technique. The EDFL produces a pulse train where the Q-switching envelope is formed by multiple dark pulses. The repetition rate of the Q-switched envelope can be increased from 0.96kHz to 3.26kHz, whereas the pulse width reduces from 211 #s to 86#s. The highest pulse of 479nJ is obtained at the pump power of 55 mW. It is also observed that the dark pulses inside the Q-switching envelope consist of two parts： square and trailing dark pulses. The shortest pulse width of the dark square pulse is obtained at 40.5μs when the pump power is fixed at 145mW. The repetition rate of trailing dark pulses can be increased from 27.62kHz to 50kHz as the pump power increases from 55mW to 145mW.

关键词： of on is as Generation of Q-Switched Mode-Locked Erbium-Doped Fiber Laser Operating in Dark Regime in

Dark pulse emission in nonlinear polarization rotation-based multiwavelength mode-locked erbium-doped fiber laser

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Chinese Optics Letters 2014年第11期12卷 119-121页

作者： Zian Cheak Tiu Sin Jin Tan harith ahmad Sulaiman Wadi Harun Department of Electrical Engineering Faculty of EngineeringUniversity of Malaya50603 Kuala Lumpur Malaysia Photonics Research Center University of Malaya50603 Kuala Lumpur Malaysia School of Engineering KDU University College SS22/41 Damansara Jaya 47400 Petaling JayaSelangor Darul Ehsan Malaysia

We experimentally show dark pulse generation in all-normal dispersion multiwavelength erbium-doped fiber laser（EDFL） with a long cavity of figure-of-eight configuration. The EDFL generates a stable multiwavelength laser with 0.47 nm spacing at 24 m W threshold pump power, while the number of lines obtained increases with the pump power. A dark pulse emission is observed as the pump power is increased above 137 m W, with fundamental repetition rate of 29 k Hz and pulse width of 2.7 μs. It is observed that the dark pulse train can be shifted to second-, third-, and fourth-order harmonic dark pulses by carefully adjusting the polarization controller. For the fundamental dark pulse, the maximum pulse energy of 32.4 n J is obtained at pump power of 146.0 mW.

关键词： mode length Dark pulse emission in nonlinear polarization rotation-based multiwavelength mode-locked erbium-doped fiber laser

Nonlinear Polarization Rotation-Based Mode-Locked Erbium-Doped Fiber Laser with Three Switchable Operation States

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Chinese Physics Letters 2014年第9期31卷 76-78页

作者： Zian Cheak Tiu Sin Jin Tan Arman Zarei harith ahmad Sulaiman Wadi Harun Department of Electrical Engineering Faculty of Engineering University of Malaya Kuala Lumpur 0603 Malaysia Photonics Research Center University of Malaya Kuala Lumpur 50603 Malaysia School of Engineering KDu University Collegel Petaling Jaya 47400 Malaysia

A simple mode-locked erbium-doped fiber laser （EDFL） with three switchable operation states is proposed and demonstrated based on nonlinear polarization rotation. The EDFL generates a stable square pulse at a third harmonic pulse repetition rate of 87kHz as the 1480 nm pump power increases from the threshold of 17.5 m W to 34.3mW. The square pulse duration increases from 105 ns to 245ns as the pump power increases within this region. The pulse operation switches to the second operation state as the pump power is varied from 48.2mW to *** W. The laser operates at a fundamental repetition rate of 29 kHz with a fixed pulse width of 8.5 μs within the pump power region. At a pump power of ***, the average output power is 3.84mW, which corresponds to the pulse energy of 131.5 ng. When the pump power continues to increase, the pulse train experiences unstable oscillation before it reaches the third stable operation state within a pump power region of 138.9 m W to 145.0 m W. Within this region, the EDFL produces a fixed pulse width of 2.8 μs and a harmonic pulse repetition rate of 58 kHz.

关键词： Pulse repetition rate

Harmonic Dark Pulse Emission in Erbium-Doped Fiber Laser

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Chinese Physics Letters 2015年第3期32卷 49-51页

作者： Zian Cheak Tiu Arman Zarei Sin Jin Tan harith ahmad Sulaiman Wadi Harun Department of ElectricM Engineering Faculty of Engineering University of Malaya Kuala Lumpur 50603 Malaysia Photonics Research Center University of Malaya Kuala Lumpur 50603 Malaysia School Of Engineering KDU University College Petaling Jaya 47400 Malaysia

A harmonic dark pulse generation in an erbium-doped fiber laser is demonstrated based on a figure-of-eight configuration. It is found that the harmonic dark pulse can be shifted from the fundamental to the 5th order harmonic by increasing the pump power with an appropriate polarization controller orientation. The fundamental repetition rate of 2O kHz is obtained at the pump power of 29 m W. The highest pulse energy of 42.6 n3 is obtained at the fundamental repetition rate. The operating frequency of the dark pulse trains shifts to 2nd, 3rd, 4th and 5th harmonic as the pump powers are increased to 34mW, 50mW, 59mW and 137mW, respectively.

关键词： Harmonic Dark Pulse Emission in Erbium-Doped Fiber Laser EDF DSF kHz