Showing papers by "Harith Ahmad published in 2003"

Double-pass L-band EDFA with enhanced noise figure characteristics

Abstract: A new double-pass long wavelength band erbium-doped fiber amplifier with enhanced noise figure characteristics is demonstrated by adding a short length of forward pumped erbium-doped fiber (EDF) in front of a double-pass amplifier. Compared with the conventional double-pass amplifier, the new amplifier provides noise figure improvement of about 0.8 to 6.0 dB over the flat-gain region from 1568 to 1600 nm. Since the optical circulator prevents the amplified signal and backward amplified spontaneous emission from propagating into the EDF, the population inversion of the input part of the amplifier is hardly affected by the intense lights, therefore, the noise figure could be kept low. The new double-pass system has achieved a flat-gain output at about 33.5 dB, which is 13.5 dB higher than that of the single-pass system with gain variation less than 1.3 dB at the flat-gain region. The noise figure varies from 5.9 to 6.6 dB in this region.

L-band Brillouin-erbium fiber laser

Abstract: The operation of the Brillouin-erbium fiber laser (BEFL) in the long wavelength band (L-band) is experimentally demonstrated. It uses a 50-m-long erbium-doped fiber (EDF) with a 400 ppm ion concentration as a gain medium to amplify the Stokes frequency signal generated in single-mode fiber (SMF). The Stokes frequency is shifted 10 GHz from its Brillouin pump with a tunability from 1598-1612 nm for a single wavelength BEFL. Multiple wavelength generation in the BEFL is realized by adding two 3-dB couplers joined in a reverse-S arrangement to take a portion of the generated BEFL signal and reinject it into the SMF to seed a cascaded BEFL line in the same direction as the first BEFL line. Twenty lines, including the anti-Stokes lines, are obtained with a maximum Brillouin pump and a 980-nm pump power of 8.8 mW and 92 mW, respectively. The L-band BEFL has the potential to be used in the future wavelength division multiplexing (WDM) communication system.

L-band erbium-doped fibre amplifier with clamped- and flattened-gain using FBG

Abstract: A gain clamped long wavelength band erbium-doped fibre amplifier (L-band EDFA) based on a ring laser cavity is demonstrated using a fibre Bragg grating (FBG) at the output end of the amplifier. This new design provides a good gain clamping as well as a gain flattening. The gain is clamped at 16.9 dB with gain variation of less than 0.1 dB from input signal power of −40 to −18 dBm by setting the VOA=5 dB. Also, the amplifier has the flattest gain spectrum at VOA=5. The gain variation is less than 1.0 dB within the wavelength range from 1570 to 1600 nm. This gain clamped amplifier also can support a 12 channel WDM system.

Gain-clamping in two-stage L-band EDFA using an unwanted backward ase from second stage

Abstract: A gain clamping technique for the long wavelength band erbium-doped fiber amplifier (L-band EDFA) is presented. It uses two circulators and a broad band fiber Bragg grating to route wasted backward C-band ASE from the second stage and launch it back into the input end of the first stage of a two-stage amplifier. The two-stage L-band EDFA has shown a small signal gain improvement of 5.7 dB compared to a single-stage amplifier with a slight noise figure degradation. By utilizing the wasted backward ASE, a L-band gain-clamped EDFA with high gain can be realized. Compared to the unclamped case, this gain-clamping technique is effective in reducing the total gain variation as small as 0.3 dB.

Gain improvement in L‐band EDFA using unpumped EDF in a double pass system

Abstract: A new gain improvement technique for L-band EDFA is presented. It uses an unpumped EDF in a double-pass configuration in order to effectively suppress and completely exploit the backward ASE. Compared to a conventional single-pass amplifier, the gain coefficient can be improved from 1.5 dB/mW to 3.1 dB/mW without much noise figure penalty. The L-band EDFA can also reduce the pump power necessary to achieve a specified gain by about half, however, this occurs at the cost of noise figure increasing by 1.6 dB. The optimum length for an unpumped EDF is experimentally measured to be 3 m for both single-pass and double-pass systems. The maximum gain improvement of 15.5 dB was observed at a signal wavelength of 1572 nm while signal and pump powers were fixed at −30 dBm and 103 mW, respectively. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 154–156, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10706

Double pass L-band erbium-doped fiber amplifier with enhanced gain characteristics

Abstract: A double pass long wavelength band (L-band) erbium-doped fiber amplifier (EDFA), which can effectively suppress and completely exploit the backward conventional band (C-band) amplified spontaneous emission (ASE) with a reflector, is presented in this paper. Circulator or broadband fiber Bragg grating (FBG) is used as the reflector to doubly passing the forward ASE and signal in the erbium-doped fiber (EDF). The gain of the double pass EDFA can be improved by about 10dB with an extra noise figure penalty of about 3dB, compared to the conventional single pass EDFA.

Gain-clamped two-stage L-band EDFA with a FBG laser in second stage

Abstract: A gain-clamped two-stage L-band EDFA is demonstrated by simply incorporating two different FBGs on both side of EDF in the second stage. It forms a FBG laser at 1560 nm to clamp the gain in the system. The gain is clamped at about 16.5 dB with gain variation of less than 1.0 dB at dynamic range up to -10 dBm. A flat gain is obtained over 30 nm of wavelength range from 1568 to 1598 nm with a gain variation of less than 1.1 dB. At the flat region, the noise figure varies from 5.0 to 5.8 dB, which is slightly higher compared to those of unclamped amplifier. The advantage of this technique is that the FBG laser does not disturb the WDM signals in the flat gain region.

Dual-Stage L-Band Erbium-Doped Fiber Amplifier for Gain Enhancement

Abstract: An experiment on gain enhancement in the long-wavelength band erbium-doped fiber amplifier (L-band EDFA) is demonstrated using a dual forward pumping scheme. Compared to a conventional single-stage amplifier, the small signal gain for a 1580 nm signal can be improved by 5.5 dB without paying much noise figure penalty. The corresponding noise figure penalty was 0.3 dB due to the insertion loss of the optical isolator. The optimum pump power ratio for the first pump was experimentally determined to be 33%. The maximum gain improvement of 8.3 dB was obtained at a signal wavelength of 1568 nm while signal and total pump powers were fixed at -30 dBm and 92 mW, respectively.

A New Gain-Clamped L-Band Erbium-Doped Fiber Amplifier with Highly Efficient Gain

Abstract: A clamped gain of 28 dB is obtained in an L-band erbium-doped fiber amplifier (EDFA) using only 84 mW of a 980 nm total pump power with 100 m EDF. Such highly efficient gain-clamped L-band EDFAs are achieved by simply adding an FBG and optical circulator to create a laser in a cavity for gain clamping. The amplifier gain is clamped at 28 dB for the dynamic range within -20 dBm with a gain variation of less than 0.2 dB. This gain-clamped amplifier also can support a 12-channel wavelength division multiplexing (WDM) system with a gain drop of less than 0.8 dB. The amplifier is expected to be able to support more channels if the laser is set at a wavelength that is within the L-band amplification region.

High gain L-band erbium-doped fiber amplifier with two-stage double-pass configuration

Abstract: An experiment on gain enhancement in the long wavelength band erbium-doped fiber amplifier (L-band EDFA) is demonstrated using dual forward pumping scheme in double-pass system. Compared to a single-stage single-pass scheme, the small signal gain for 1580 nm signal can be improved by 13.5 dB. However, a noise figure penalty of 2.9 dB was obtained due to the backward C-band ASE from second stage and the already amplified signal from the first pass that extracting energy from the forward C-band ASE. The maximum gain improvement of 13.7 dB was obtained at a signal wavelength of 1588 nm while signal and total pump powers were fixed at -30 dBm and 92 mW, respectively.

Effect of injection of C-band ASE on L-band erbium-doped fiber amplifier

Abstract: The effect of injecting conventional band (C-band) amplified spontaneous emission on the performance of long-wavelength band erbium-doped fiber amplifier (L-band EDFA) is demonstrated. It uses a circulator and broadband fiber Bragg grating (FBG) to route C-band ASE from a C-band EDFA. Injection of a small amount of ASE (attenuation of 20 dB or above) improves the small signal gain with a negligible noise figure penalty compared to that of an amplifier without the ASE injection. A maximum gain improvement of 3.5 dB is obtained at an attenuation of 20 dB. At very large amounts of ASE injection (attenuation of 0 dB), the gain of the amplifier is clamped at 15.2 dB from −40 to −10 dBm with a gain variation of less than 0.3 dB. The saturation power is also increased from −8 dBm (for without ASE injection) to 2 dBm (VOA=0 dB) with a slight noise figure penalty. These results show that the ASE injection technique can be used either for gain improvement or for gain clamping in L-band EDFA.

Gain clamped L‐band EDFA using a fiber Bragg grating in two stage configuration

Abstract: A gain clamping technique for the long-wavelength-band erbium-doped fiber amplifier (L-band EDFA) is presented. It uses two circulators and a fiber Bragg grating (FBG) to route a backward amplified spontaneous emission (ASE) from a second-stage amplifier and launch it back into the first stage. The use of a broadband (BB) FBG has shown a better gain clamping effect, compared to a narrowband (NB) FBG. The amplifier gain for the BB FBG set up is clamped at 15.0 dB with a gain variation of less than 0.1 dB for an input power as high as −5 dBm. The use of a BB FBG has also flattened the gain spectrum. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 265–266, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10889

Gain-Clamped L-Band Erbium-Doped Fiber Amplifier with Co- and Counter-Propagating Lasers

Abstract: The long-wavelength-band (L-band) gain-clamped erbium-doped fiber amplifier with a co- and counter-propagating ring lasers is investigated. The ring laser at 1566 nm is formed with a C/L-band wavelength division multiplexing (WDM) coupler. This new technique has shown a good gain-clamping effect with gain variation of less than 0.2 dB for input signal powers from -40 to -14 dBm. Compared with an unclamped amplifier, the noise figures for small signals are improved due to the suppression of backward ASE. The amplifier with a co-propagating laser has shown a better gain and noise figure compared to with a counter-propagating laser. The advantage of both gain-clamped systems is that oscillating light does not appear at the output port of the amplifier.

Gain and noise performances of an L-band EDFA utilizing a ring laser cavity with fiber Bragg grating

Abstract: The performances of gain and noise figure of an L-band EDFA utilizing a ring laser cavity is demonstrated. It uses a fiber Bragg grating (FBG), arranged to propagate in opposition to the amplifier signal by a pair of circulators, to provide laser feedback. A flat-gain spectrum with less than 1.1-dB variation between 1568 nm and 1604 nm was observed with the laser wavelength at 1560 nm. A gain-clamping effect was also observed with this configuration, which provided a constant gain for all tested input signal powers from -40 dBm to 0 dBm.

Gain clamping in dual-stage L-band EDFA by recycling a backward ASE

Abstract: Gain clamping in dual-stage long-wavelength (L-band) erbium-doped fiber amplifier (EDFA) is demonstrated It uses two circulators and a broadband fiber Bragg grating (FBG) to route a wasted backward conventional band (C-band) amplified spontaneous emission (ASE) from the second stage and launch it back into the input end of the first stage The amplifier gain is clamped at 165 dB with variation less than 02 dB and the dynamic range up to -75 dBm for the VOA loss of 4 dB The clamped gain level also can be controlled from 150 to 229 dB by increasing the VOA loss from 0 to 32 dB without much variation in noise figure

Injection locking of an erbium‐doped fiber laser‐amplifier

Abstract: Injection locking of an erbium-doped fiber laser-amplifier is presented. Inside the locking range, the system oscillates at the wavelength of the injected signal. Outside the locking range, both signal and laser oscillate simultaneously in the cavity. Signal detuning studies show that the locking range increases with higher input signal power. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 89–91, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10683

Two-stage L-band erbium doped fiber amplifier

Abstract: Gain enhancement in a long-wavelength band erbium-doped fiber amplifier (L-band EDFA) is demonstrated using isolator to split the erbium-doped fiber (EDF) into two segments. Both segments are pumped separately using a dual forward pumping scheme. Compared to a conventional single- stage amplifier, the small signal gain for a 1580 nm signal can be improved by 5.5 dB without paying much noise figure penalty. The corresponding noise figure penalty was 0.3 dB due to the insertion loss of the optical isolator. The maximum gain improvement of 8.3 dB was obtained at a signal wavelength of 1568 nm while signal and total pump powers were fixed at -30 dBm and 92 mW, respectively.

Double pass L-band EDFA with an improved gain coefficient

Abstract: A new double pass long wavelength hand erbium-doped fibre amplifier (L-band EDFA) with an improved gain is demonstrated by unpumping of the first 5 m of the EDF. The wasted conventional band (C-band) backward amplified spontaneous emission (ASE) was used as a secondary pump source for the unpumped EDF. Our experimental results have shown that, compared to a conventional double pass amplifier, the gain coefficient can be improved considerably from 0.24 dB/mW to 0.40 dB/mW. The new amplifier uses only 67% of the pump power to achieve a gain value equal to that for the conventional amplifier. The maximum gain enhancement of 22.5 dB was observed at a signal wavelength of 1568 nm of while signal and pump powers were fixed at -30 dBm and 62 mW, respectively.

Double Pass L-Band EDFA with Unpumped EDF

Abstract: A new double pass long wavelength band erbium-doped fibre amplifier (L-band EDFA) with a further improved gain is demonstrated using double pass technique with a first 5 m of the EDF is unpumped. The wasted conventional band (C-band) backward amplified spontaneous emission (ASE) is used as a secondary pump source for the unpumped EDF. Our experimental results have shown that, compared to a conventional double pass amplifier, the gain coefficient can be improved considerably from 0.24 dB/mW to 0.40 dB/mW. The new amplifier uses only 67% of the pump power to achieve a gain value equal to that for the conventional amplifier. The maximum gain enhancement of 22.5 dB was observed at a signal wavelength of 1568 nm of while signal and pump powers were fixed at -30 dBm and 62 mW, respectively.

Comparison of Performances Between Two-stage and Single-stage L-Band EDFA

Abstract: Gain enhancement in a long wavelength (L-band) erbium-doped fiber amplifier (EDFA) using a two-stage configuration with dual forward pumping scheme is demonstrated. Compared to a conventional single-stage amplifier, the two-stage amplifiers can improve the small signal gain over the wavelength region from 1560 to 1612 nm. A maximum gain enhancement of 9.6 dB is obtained for a two-stage type II amplifier at the signal wavelength of 1568 nm. The corresponding noise figure is also improved by 0.2 dB.

Gain Enhancement in L–Band EDFA by Splitting EDF into Two Stages

Abstract: Sebuah esperimen bagi menambah daya pembesaran untuk jalur gelombang panjang (jalur–L) pembesar terdop erbium (PTE) telah didemonstrasi menggunakan reka bentuk yang berbadan dua. Jika dibandingkan dengan pembesar yang berbadan satu, pembesar ini dapat menambah pembesaran untuk isyarat 1580 nm sebanyak 5.5 dB dengan sedikit sahaja penambahan nilai bisingan. Nilai bisingan bertambah sebanyak 0.3 dB kerana kemasukan isolator dalam reka bentuk. Kadar kuasa pam pertama mestilah 33% daripada jumlah keseluruhan kuasa pam untuk nilai optima. Pembesaran maksimum sebanyak 8.3 dB telah diperolehi oleh isyarat 1568 nm semasa kuasa isyarat dan kuasa pam, masing–masing ditetapkan pada 30 dBm dan 92 mW. Keputusan esperimen menunjukkan penggunaan pembesar berbadan dua dapat menjimatkan kos kerana ia menggunakan kuasa pam yang lebih rendah. Kata kunci: Gentian terdop erbium, pembesar optik, pembesar terdop erbium, jalus LPTE An experiment on gain enhancement in the long–wavelength band erbium–doped fiber amplifier (L–band EDFA) is demonstrated using a dual stage configuration. Compared to a conventional single–stage amplifier, the small signal gain for a 1580 nm signal can be improved by 5.5 dB without paying much noise figure penalty. The corresponding noise figure penalty was 0.3 dB due to the insertion loss of the optical isolator. The optimum pump power ratio for the first pump was experimentally determined to be 33%. The maximum gain improvement of 8.3 dB was obtained at a signal wavelength of 1568 nm while signal and total pump powers were fixed at –30 dBm and 92 mW, respectively. These results show that the employment of the dual–stage amplifier system will play an important role in the development of a practical L–band EDFA from the perspective of economical usage of pump power. Key words: Erbium doped fiber, optical amplifier, L-band EDFA, dual-stage EDFA, amlified spontaneous emission

10-GHz optical comb in L-band region with brillouin/erbium-doped fibre laser

Abstract: A multiwavelength Brillouin/erbium fibre laser (BEFL) which operates in the long wavelength (L-band) region is demonstrated for potential applications in an L-band wavelength division multiplexing (WDM) communication system. The laser configuration consists of a long erbium-doped fibre to enable L-band amplification where two 3-dB couplers take a portion of the generated BEFL signal and re-inject it into the single mode fibre to seed a cascaded BEFL line in the same direction as the first BEFL line. A stable and strong laser comb of up to five lines with 10-GHz spacing has been obtained with a Brillouin pump (BP) of 9.2 mW and a 980 nm pump of 92 mW. The BEFL has shown a broad tuning range with a tuning characteristic for line #1 which is flat over a range greater than 9.9 nm.