Comparison of 1480 nm and 980 nm-pumped Gallium-Erbium fiber amplifier

Background: One way to reduce the length of the gain medium in Erbium-Doped Fiber Amplifier (EDFA) is by doping the fiber core with a high concentration of Erbium. However, this method caused ion clustering effects, which limits the EDFA’s efficiency. In this research, the use of Gallium as a new co-dopant in erbium-doped silica fiber is explored. Methods: The new fiber, namely Gallium co-doped Erbium fiber (Ga-EDF), is used as a gain medium in an optical fiber amplifier setup. A 2-meter length of the Ga-EDF fiber was used in a single pass configuration with a forward pumping scheme at 150 mW pump power. The Ga-EDF amplifier's gain and noise figure while pumping at 980 nm and 1480 nm were compared. The amplifier's performance was evaluated as the input signal power varied between -30 dBm to 3 dBm, over the wavelength range of 1520 nm to 1580 nm. Results: The 980 nm-pumped Ga-EDF amplifier achieved the maximum small-signal gain of 22.45 dB and the corresponding noise figure of 5.71 dB at the input signal wavelength of 1535 nm. Meanwhile, the 1480 nm-pumped Ga-EDF amplifier attained the maximum small-signal gain of 20.83 dB and the corresponding noise figure of 5.09 dB at the input signal wavelength of 1550 nm. At the input signal power below -20 dBm and the wavelength range 1520 nm to 1547 nm, the Ga-EDF performs better when pumped at 980 nm. Their performance is comparable at the input signal wavelength range between 1547 nm to 1580 nm. At the input signal power above -20 dBm, the 1480 nm-pumped Ga-EDF outperformed the 980 nm-pumped amplifier. Conclusions: The overall performance indicates that the gain saturation point of the 1480 nm-pumped amplifier is higher than the 980 nm-pumped.

Investigating the performance of all-optical AND logic gate based on FWM effect in SOA at low power

In the present work, the performance of the all-optical AND logic gate using four wave mixing in wide band semiconductor optical amplifier (SOA) has been analyzed for different modulation formats. The two binary inputs of all-optical AND gate are modulated by return to zero and non-return to zero (NRZ) modulation formats. The quality factor (Q-factor) has been examined on the basis of critical parameters of SOA. The obtained results show that the acceptable Q-factor (>6) is possible with the proposed design at input signal power even as low as 50 μW (−13 dBm), when the data is modulated in NRZ on-off keying (OOK) format.

EDFA gain flattening optimization with long period fiber gratings in WDM system

This paper highlights a proposed optimized gain flatness technique for nonuniform gain spectrum of the erbium-doped fiber amplifier (EDFA) by introduction of long period fiber gratings (LPFG). In this analysis, EDFA gain spectrum has been evaluated between 1525 and 1600 nm with −20 dBm input signal power. Attenuation peaks of LPFG are optimized with a grating period of 240 µm and grating length of 30000 µm in the wavelength range of 1.1–1.8 μm, to compensate the peak gain of EDFA. Results have shown that EDFA peak gain of 35.94 dB is achieved at 1532.89 nm wavelength. This 35.94 dB peak gain is flattened up to 2.65 dB using long period fiber gratings. Also, less than ±0.3 dB gain flatness is achieved between 1528 and 1560 nm wavelength. The proposed less complex technique can be used to modify the grating parameters during fabrication in order to produce the loss peak at desired wavelength, which is efficient to flatten EDFA gain peak.

Comparison of 1480 nm and 980 nm-pumped Gallium-Erbium fiber amplifier

Background: One way to reduce the length of the gain medium in Erbium-Doped Fiber Amplifier (EDFA) is by doping the fiber core with a high concentration of Erbium. However, this method caused ion clustering effects, which limits the EDFA’s efficiency. In this research, the use of Gallium as a new co-dopant in erbium-doped silica fiber is explored. Methods: The new fiber, namely Gallium co-doped Erbium fiber (Ga-EDF), is used as a gain medium in an optical fiber amplifier setup. A 2-meter length of the Ga-EDF fiber was used in a single pass configuration with a forward pumping scheme at 150 mW pump power. The Ga-EDF amplifier's gain and noise figure while pumping at 980 nm and 1480 nm were compared. The amplifier's performance was evaluated as the input signal power varied between -30 dBm to 3 dB, over the wavelength range of 1520 nm to 1580 nm. Results: The 980 nm-pumped Ga-EDF amplifier achieved the maximum small-signal gain of 22.45 dB and the corresponding noise figure of 5.71 dB at the input signal wavelength of 1535 nm. Meanwhile, the 1480 nm-pumped Ga-EDF amplifier attained the maximum small-signal gain of 20.83 dB and the corresponding noise figure of 5.09 dB at the input signal wavelength of 1550 nm. At the input signal power below -20 dBm and the wavelength range 1520 nm to 1547 nm, the Ga-EDF performs better when pumped at 980 nm. Their performance is comparable at the input signal wavelength range between 1547 nm to 1580 nm. At the input signal power above -20 dBm, the 1480 nm-pumped Ga-EDF outperformed the 980 nm-pumped amplifier. Conclusions: The overall performance indicates that the gain saturation point of the 1480 nm-pumped amplifier is higher than the 980 nm-pumped.

Free space and wired optics communication systems performance improvement for short-range applications with the signal power optimization

This article discusses the performance of the free space optics (FSO) systems for short-range applications with the input signal power optimization. The BER eye diagram analyzer used to compute the optimum bit error rate and also compute the maximum Q factor for the previous and proposed models. The previous model has outlined the maximum Q factor of 206.45, where the proposed model Q factor value is 569.867 under the same operating parameters such as the wavelength of the transmitter of 1550 nm, the power of the transmitter of 10 mW, and the range of FSO is 800 m and signal attenuation 0.4 dB/km. The proposed study has outlined better performance than the previous study by about 21.76% enhancement percentage ratio.

Widely Flatness Gain Bandwidth with Double Pass Parallel Hybrid Fiber Amplifier

A Widely flatness gain bandwidth with double pass parallel hybrid fiber amplifier is experimentally demonstrated in this study. The proposed design combines serial erbium–Raman fiber amplifier in one branch and Raman fiber amplifier in the second branch. Multiple Raman pump units with a maximum power of 800 mW (250 mW of 1410 nm, 225 mW of 1480 nm, and 325 mW of 1495 nm) are utilized. Pump recycling technique is applied to achieve acceptable pumping efficiency. A maximum flatness gain bandwidth of 80 nm (1525–1605 nm) and average gain level of 22.5 dB are obtained at a small input signal power of -25 dBm and optimum pump power values. By comparison, a wider flatness gain of 90 nm (1520–1610 nm) and average gain level of 11.5 dB are achieved at a large input signal power of -5 dBm.

Performance analysis on double-pass thulium-doped fiber amplifier for 16-channel WDM system at S-band

In this paper, the performance of single and double-pass thulium-doped fiber amplifiers (SD-TDFA and DP-TDFA) is analyzed in the short wavelength (S-band) region. The effect of thulium-doped fiber (TDF) length, input signal power, and input pumping power on the amplifier’s performance is comprehensively investigated on basis of gain and noise figure (NF). DP-TDFA showed a higher gain compared to single-pass configuration and that is due to double-propagation of the forwarded and amplified spontaneous emission (ASE) signal into the TDF which maximizes the achievable gain in the S-band region. At a gain medium length of 8 m, the proposed DP-TDFA showed higher gain enhancement over SP-TDFA at an input power of −20 dB compared to −40 and 0 dB input signal powers. The gain enhancement at 1470 nm is 5.6 dB, while the maximum recorded gain with the proposed double-pass configuration is 14.7 dB.

Characteristics of Dispersion Compensation for 32 Channels at 40 Gb/s Under Different Techniques

In this study, a simulation analysis of 40-Gb/s long-haul (120 km) dense wavelength-division multiplexer system (DWDM) of 32 channels with 50 GHz spacing is conducted for duobinary return-to-zero modulation formats. Pre- and post-dispersion compensation schemes utilizing dispersion compensating fiber (DCF) and fiber Bragg grating (FBG) are analyzed to compare these schemes at high bit rate. Quality factor (Q) and bit error rate (BER) values are used to measure the response of the system as a function of input power for both compensation schemes. The pre-FBG scheme shows a better performance in terms of Q-factor that reached 11.5 at 0 dBm input signal power.

Nonlinearities Diminution in 40 Gb/s 256 QAM Radio over Fiber Link via Machine Learning Method

Machine learning (ML) methodologies have been looked upon recently as a potential candidate for mitigating nonlinearity issues in optical communications. In this paper, we experimentally demonstrate a 40-Gb/s 256-quadrature amplitude modulation (QAM) signal-based Radio over Fiber (RoF) system for 50 km of standard single mode fiber length which utilizes support vector machine (SVM) decision method to indicate an effective nonlinearity mitigation. The influence of different impairments in the system is evaluated that includes the influences of Mach-Zehnder Modulator nonlinearities, in-phase and quadrature phase skew of the modulator. By utilizing SVM, the results demonstrated in terms of bit error rate and eye linearity suggest that impairments are significantly reduced and licit input signal power span of 5dBs is enlarged to 15 dBs.