Makhfudzah Mokhtar

Seamless tuning range based-on available gain bandwidth in multiwavelength Brillouin fiber laser.

We experimentally demonstrate a simple widely tunable multiwavelength Brillouin/Erbium fiber laser that can be tuned over the entire C-band, thereby greatly improving the tuning range limitation faced by the previous Brillouin-erbium fiber laser architectures. Tuning range of 39 nm from 1527 nm to 1566 nm, which is only limited by the amplification bandwidth of the erbium gain was successfully achieved. At Brillouin pump wavelength of 1550 nm and 1480 nm laser pump and Brillouin pump powers of 130 mW and 2 mW respectively, all the generated output channels have peak power above 0 dBm, with the first output channel having a peak power of 8.52 dBm. The experimental set up that consists of only 4 optical components, is simple, devoid of the complex structure employed previously to enhance the tunability and feedback mechanism normally associated with multiwavelength Brillouin-erbium fiber laser sources. The generated output channels are stable, rigidly separated by 10 GHz (0.08 nm).

20 GHz spacing multi-wavelength generation of Brillouin-Raman fiber laser in a hybrid linear cavity

We demonstrate a tunable multi-wavelength Brillouin-Raman fiber laser with 20 GHz wavelength spacing. The setup is arranged in a linear cavity by employing 7.2 and 11 km dispersion compensating fibers (DCF) in addition to a 30 cm Bismuth-oxide erbium doped fiber. In this experiment, for the purpose of increasing the Stokes lines, it is necessary to optimize Raman pump power and Brillouin pump power together with its corresponding wavelengths. At the specific Brillouin pump wavelength, it is found that the longer length of 11 km DCF with optimized parameters results in larger number of Stokes combs and optical signal to noise ratios (OSNRs). In this case, a total of 195 Brillouin Stokes combs are produced across 28 nm bandwidth at Brillouin pump power of -2 dBm and Raman pump power of 1000 mW. In addition, all Brillouin Stokes signals exhibit an average OSNR of 26 dB.

Duty-cycle division multiplexing (DCDM)

A multiplexing technique, which is based on duty-cycle division, is proposed. The channel multiplexing and demultiplexing are performed electrically at the single user bit rate, which is very economic. In a three-user system (3×10 Gb/s), the simulation results show that the best receiver sensitivity value achieved is −30.1 dBm with an optical signal-to-noise ratio (OSNR) of 22.3 dB, while the chromatic dispersion tolerance ranges from 192 to 280 ps/nm. Migration from 30 to 120 Gb/s is achieved with the penalty of 6.4 and 5.2 dB in the receiver sensitivity and OSNR, respectively, for the worst user.

Multi-wavelength Brillouin-Raman fiber laser utilizing enhanced nonlinear amplifying loop mirror design

We demonstrate a single-spacing, multi-wavelength Brillouin-Raman fiber laser utilizing an enhanced cavity of nonlinear amplifying loop mirror. In this structure, the optimization of multi-wavelength lasing is done with proper adjustments of coupling ratio and Brillouin pump power. When setting the Raman pump power to 300 mW, up to 28 channels with an average 17 dB optical signal-to-noise ratio are achieved. In this case, the Brillouin pump power is maintained at -2.6 dBm when the splitting ratio and Brillouin pump wavelength are fixed at 99/1 and 1555 nm, correspondingly. Our achievements present high numbers of Stokes channels with an acceptable optical signal-to-noise ratio at low pump power operation.

Broadly tunable multiple wavelength Brillouin fiber laser exploiting erbium amplification

We experimentally demonstrate a highly stable and flawless-tuning-range multiple wavelength Brillouin fiber laser incorporating an erbium gain block. Free-running cavity modes that inherently circulate in the cavity of a Brillouin/erbium fiber laser, which limits wavelength tunability, are completely suppressed. At a Brillouin pump power of 2 mW and 130 mW of 1480 nm pump power, we obtained seven output channels. The tunability of the generated channels is only limited to 35 nm by the amplification bandwidth of the erbium gain used in the experiment. The first four channels have an output power each above 1.6 dBm with the first and the seventh channels having a peak power of 8.19 dBm and −8.30 dBm.

150-Channel Four Wave Mixing Based Multiwavelength Brillouin-Erbium Doped Fiber Laser

A wide band tunable multiwavelength Brillouin-erbium fiber laser (BEFL) is developed. In this structure, the laser is formed between a double pass amplification box and a highly nonlinear fiber (HNLF), which acts as a virtual mirror, results in removing the reflective physical mirror from one side of the laser structure. A large number of Stokes and anti-Stokes lines are generated through cascading stimulated Brillouin scattering and inducing four wave mixing process inside the HNLF. Due to optimizing Brillouin and erbium doped fiber (EDF) pump powers, the Rayleigh back scattering is efficiently suppressed, and the generated BEFL wavelengths are free from self lasing cavity modes over a wide tuning range. At EDF pump power and Brillouin pump power of 100 mW and 3 dBm, respectively, up to 150 Stokes lines with wavelength spacing of 0.076 nm, and a tuning range of 40 nm were achieved.

Utilization of stimulated Raman Scattering as secondary pump on hybrid remotely-pump l-band Raman/erbium-doped fiber amplifier

An L-band remotely-pumped erbium-doped fiber amplifier incorporating a secondary pumping scheme utilizing stimulated Raman Scattering (SRS) was demonstrated. 1423 nm Raman laser was employed to generate SRS which became the secondary pump source. The amplifier displayed excellent gain of up to 27.3 dB at 1570 nm for −30 dBm input. Noise figures were also kept to a minimum, with the highest figure measured at 11 dB which was influenced by imperfection of the C/L coupler utilized in this architecture. Overall transmission performance was measured as well and demonstrated an encouraging outcome with gain as high as 24 dB while the noise figure was maintained at about 11 dB. The L-band signal amplification was also contributed by the stimulated Raman scattering along the transmission fiber. The outcome of this study emphasized the feasibility of secondary pumping scheme using SRS in L-band gain enhancement.

Compact Brillouin Fiber Laser Based on Highly Nonlinear Fiber With 51 Double Spacing Channels

A compact multiwavelength Brillouin fiber laser (BFL) with 51 stable double Brillouin frequency shift channels is demonstrated at room temperature. It uses a ring cavity with a 3-dB coupler for separation of odd-ordered and even-ordered Brillouin Stokes (BS) channels using a highly nonlinear fiber (HNLF) as the Brillouin gain medium. Compared with the use of a standard single-mode fiber, the HNLF-based BFL produces higher output power and a higher count of Stokes lines. At the maximum Brillouin pump (BP) power of 16.7 dBm, 36 odd channels and 15 even channels are generated with a channel spacing of 0.15 nm. The output power of the even channels is observed to be always lower than that of the odd channels as they are generated from the previous odd BS.

Performance analysis of a variable-weight OCDMA system under the impact of fiber impairments

The impact of Chromatic Dispersion (CD) and Non-Linear Effects (NLE) including Self-Phase Modulation (SPM) and Four-Wave Mixing (FWM), on the performance of a Variable-Weight Optical Code Division Multiple Access (VW-OCDMA) system at 1.25 Gbps is analyzed by simulation. The results show that CD is the most dominant effect, which increases the users bit error rate (BER) especially for the users with higher weights. In order to investigate the performance of system in service differentiation for users with different weights, Dispersion Compensating Fiber (DCF) is used to mitigate the effect of CD caused by Single Mode Fiber (SMF). The results show that users with higher weights have better performance as expected and impact of NLE is negligible for distance up to 150 km, considering low launched power.

Multiple access interference elimination with enhanced chromatic dispersion tolerance in SAC OCDMA

We demonstrate a direct decoding scheme to eliminate multiple access interference in optical spectral-amplitude-coded, multiple access networks. By detecting only the non-overlapping spectrums, our scheme shows a better BER of eight orders of magnitude over the conventional complementary subtraction scheme, when 16 simultaneous channels with 10Gbps bit rate per channel are transmitted over a simulated 70km dispersion-compensated fiber span. Our direct decoding technique is also tolerant to chromatic dispersion, where the maximum achievable distance of 67km was obtained in a dispersion limited system with standard 16ps/nm.km dispersion of single mode fiber.