Design and Analysis of Quaternary to Binary Radix Converter Using SOA-PRS

Abstract

This paper reports a new design of a quaternary to binary radix converter. Semiconductor optical amplifier-based polarization rotation switches (SOA-PRS) have been used for the basic switching element in the design. A dual-SOA structure is utilized to design the circuit. The design is simple, made off only two SOAs. The circuit performance has been analyzed with a Gaussian pulse train, and the extinction ratio has been calculated. The simulation work is done at an ultra-high data rate (100 Gb/s). SOA-based design is simple and compact than other switching structures. The SOA-PRS works on the principle of the cross-polarization modulation (XpolM) effect.

Appendix

The Gaussian-shaped output pulses used in each of the input signals of the circuit can be expressed in Eq. 1 as,

$$\begin{aligned} P & = P_{0} \mathop \sum \limits_{i} \exp \left( {\frac{{t_{i}^{2} }}{{\sigma^{2} }}} \right) \\ {\text{where}},\,P_{0} & = \frac{1}{\sigma \sqrt \pi }\,{\text{and}}\,\sigma = \frac{T}{1.665}. \\ \end{aligned}$$

(1)

where, $P_{0}$, T and t represent “maximum power”, “full width at half maximum (FWHM)” and the “bit-period” respectively.

A time-dependent solution of the rate equation is utilized. The output power of the polarization rotation switch from Port-1 is given by [14, 15]

$$P_{{{\text{out}}}} = P^{{{\text{TE}}}} + P^{{{\text{TM}}}} - 2\sqrt {P^{{{\text{TE}}}} P^{{{\text{TM}}}} } \cos \left(\uptheta \right)$$

(2)

where, P^TE and P^TM are the respective intensities of TE and TM components of the output probe signal. $\uptheta$, is the phase difference between TE and TM components.

The small peaks arise due to the noise effects produced by the SOA’s and mainly the Amplified Spontaneous Emission effect [17, 21] expressed as (Eq. 3),

$$P_{{{\text{ASE}}}} = N_{{{\text{SP}}}} . h. \, \left( {G - 1} \right) \, B$$

(3)

where, G is the gain, h Planck^’s constant, B optical bandwidth of a filter within which P_ASE is determined, N_spis the spontaneous emission factor or noise factor (~1 for ideal amplifier).

The Extinction Ratio [17] of the design can be calculated using Eq. 4,

$${\text{ER}} = 10.\log_{10} \left( {\frac{{P_{1}^{\min } }}{{P_{0}^{\max } }}} \right)$$

(4)

where $P_{1}^{\min }$ represents the minimum power in high state 1 and $P_{0}^{\max }$ represents the maximum power in low state 0. The plots of the ER versus pump power at different probe power and noise factor are shown in Figs. 6 and 7 respectively in the “Results and Discussion” section.