**3. Design and model of SOA and FRA circuit**

The suitable amplifier is one way to deal with the effects of linear and nonlinear disturbances as well as maximize the working of optical transmission media. Generally the optical amplifier consists of fiber Raman amplifier (FRA), erbium-doped fiber amplifier (EDFA), and semiconductor optical amplifier (SOA). SOA is designed in the form of quantum-dot SOA network as linear network and bulk SOA as nonlinear network [2]. Then, it is known that SOA has a high nonlinear nature, low power consumption, fast operating speed, and can easily be used in photonic systems [6–9].

In SOA type amplifier, the gain can be calculated using the following equation:

$$\mathbf{g}\_{\mathcal{W}} = \mathcal{A}\_{\mathcal{\tilde{\mathcal{K}}}} (N - N\_0) \tag{1}$$

BER and Q-factor are the most important factors that limiting the transmission distance in optical communication system. In order to transmit signals over long distances, it is necessary to have a low BER and high Q-factor within the fiber. The optical amplifier in the fiber represents the optical signals to be directly amplified optically without any conversion. The BER is an indication of how often data is retransmitted due to an error. Too high BER may indicate that a slower data rate will actually improve overall transmission time for a given amount of transmitted data because the BER may be decreased, lowering the quantity of packets that has to be present. In BER, the quantity of measured bits is incorrect before error correction, divided by the total amount of transferred bits (including redundant error codes). Usually, the BER is larger than the information data of it. The information of BER is influenced by the strength of the forward error correction program and code. There are kinds of BER occurring in optical communication circuit. It can be affected by transmission noise, interference, distortion, bit synchronization problems, attenuation, wireless multipath fading, etc. However, in

Optical Amplifiers for Next-Generation Telecommunication

http://dx.doi.org/10.5772/intechopen.79941

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both amplifiers, we consider the simple channel model and data source model.

and characterizes a resonator's bandwidth relative to its center frequency.

**3.1. Information source block**

source of pulse information.

**Figure 5.** Model design with amplifier.

Another factor is Q-factor, which explains the resonance performance of disturbance that is particularly shown by an underdamped harmonic oscillator. The driven cavity or resonators having high number of Q-factor will resonate with larger intensity, which is shown by amplitudes (at certain frequency). They have more tiny bandwidth range of frequencies around that frequency. They will resonate having frequencies that are defined as a bandwidth. The high value of Q-factor oscillators oscillates with more tiny range of frequencies and more stable condition. Q-factor unit is dimensionless describing how underdamped an oscillator is

The design of the network model will be simulated using OptiSystem version 11.1.0.53. In the model, the SOA and FRA optical amplifiers are coupled to the transmission amplifier network (in-line amplifier). **Figure 5** shows the design of model, optical fiber communication system.

The information source block consists of two components: pseudorandom bit sequence (PRBS) and *non-return-to-zero pulse generator* (NRZ). PRBS functions to generate bits with specific patterns and speeds. Then the bit that has been generated by PRBS will be encoded using NRZ coding technique. NRZ coding technique has the advantage that is more resistant to noise and is not affected by the voltage level. **Figure 6** shows the planning drawing for the

where *gm* = material amplifier, *Ag* = coefficient of derivative gain, *N* = carrier density, *N<sup>o</sup>* = carrier density at the point of transparency.

$$\mathbf{g}\_t \quad \mathbf{l} \mathbf{\hat{g}}\_n - \alpha \tag{2}$$

where *g<sup>t</sup>* = coefficient of amplifier, *Γ* = optical confinement factor, α = effective loss coefficient.

$$G = \exp[\mathbf{g}\_t \mathbf{z}] \tag{3}$$

where *G* = magnitude of gain (dB), *z* = length of optical fiber (dB).

Then, Bromage introduced the RA used in fiber-optic communication systems [10]. The gain on this amplifier can be calculated using the equation as follows:

$$G = 10\left|\log(\exp|\lg\mathcal{V}\_{\cdot}|)\right.\tag{4}$$

$$\log = 2\chi p \operatorname{Im}(\mathcal{Z}\_{1111}|\alpha\_{\flat} - \alpha\_{\natural}|) \tag{5}$$

$$
\gamma - \frac{2\pi m\_2}{\mathcal{A}\mathcal{A}\_{\text{eff}}} \tag{6}
$$

where *G* = magnitude of gain (dB), *P* = power pump (Watt), *L* = length of optical fiber (m), *n<sup>2</sup>* = nonlinear refractive index (m<sup>2</sup> . W−<sup>1</sup> ), *γ* = nonlinear phase change (rad), *Aeff* = effective surface (m2 ), *λ* = wavelength signal (m), *g* = Raman gain coefficient, *ρ* = nonlinear polarization fraction, *Χ1111(ω<sup>p</sup> – ω<sup>s</sup> )* = Raman's susceptibility.

Both amplifiers show that the type of SOA more considered the carrier density and the material factor, whereas FRA more considered the frequency characteristics and wave nonlinear conditions. However, both amplifiers are very dependent on the media passed by the signal. In order to investigate the performance of SOA and FRA, bit error rate (BER) and Q-factor are two parameters used to measure their characteristics.

BER and Q-factor are the most important factors that limiting the transmission distance in optical communication system. In order to transmit signals over long distances, it is necessary to have a low BER and high Q-factor within the fiber. The optical amplifier in the fiber represents the optical signals to be directly amplified optically without any conversion. The BER is an indication of how often data is retransmitted due to an error. Too high BER may indicate that a slower data rate will actually improve overall transmission time for a given amount of transmitted data because the BER may be decreased, lowering the quantity of packets that has to be present. In BER, the quantity of measured bits is incorrect before error correction, divided by the total amount of transferred bits (including redundant error codes). Usually, the BER is larger than the information data of it. The information of BER is influenced by the strength of the forward error correction program and code. There are kinds of BER occurring in optical communication circuit. It can be affected by transmission noise, interference, distortion, bit synchronization problems, attenuation, wireless multipath fading, etc. However, in both amplifiers, we consider the simple channel model and data source model.

Another factor is Q-factor, which explains the resonance performance of disturbance that is particularly shown by an underdamped harmonic oscillator. The driven cavity or resonators having high number of Q-factor will resonate with larger intensity, which is shown by amplitudes (at certain frequency). They have more tiny bandwidth range of frequencies around that frequency. They will resonate having frequencies that are defined as a bandwidth. The high value of Q-factor oscillators oscillates with more tiny range of frequencies and more stable condition. Q-factor unit is dimensionless describing how underdamped an oscillator is and characterizes a resonator's bandwidth relative to its center frequency.

The design of the network model will be simulated using OptiSystem version 11.1.0.53. In the model, the SOA and FRA optical amplifiers are coupled to the transmission amplifier network (in-line amplifier). **Figure 5** shows the design of model, optical fiber communication system.
