**4. Power consumption in SOA-based optical packet switches**

High capacity routers system designer are facing with power consumption issues. Today commercial products that can follow the increase in capacity demand for packet switched networks are based on multirack equipment. Optical packet switching (OPS) (Ben Yoo, 2011) systems could lead to solve this issue providing a solution that could be compact, fast, and power efficient. Next we propose some models to investigate the power consumption 8 Optical Amplifier

**S S**

**S S**

**S S**

**S S**

Fig. 9. BENES Optical Packet Switch realized with splitters, couplers and SOAs (*N*=2, *M*=2,

adjacent stages with a 3dB Directional Coupler (DC) the output couplers on the left-hand and

**D C D C**

**D C D C**

**D C D C**

**D C D C**

Fig. 10. BENES Optical Packet Switch realized with splitters, directional couplers, couplers

High capacity routers system designer are facing with power consumption issues. Today commercial products that can follow the increase in capacity demand for packet switched networks are based on multirack equipment. Optical packet switching (OPS) (Ben Yoo, 2011) systems could lead to solve this issue providing a solution that could be compact, fast, and power efficient. Next we propose some models to investigate the power consumption

**Control signals**

**Amplifier (SOA)** 1

**Semiconductor Optical Amplifier (SOA)**

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and SOAs (*N*=4, *M*=2, *r*=2).

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O*1*

O*2*

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the input splitters on the right-hand.

O*1*

O*2*

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**4. Power consumption in SOA-based optical packet switches**

**C C**

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1

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of Optical Packet Switching. First of all we introduce a SOA's power consumption model in Section 4.1 able to evaluate the power consumption as a function of the main SOA's parameters (current, forward polarization voltage, material loss, gain,··· ). Analytical models are introduced in Section 4.2 to evaluate the power consumption of Synchronous SPN (SSPN) Optical Packet Switches equipped with SS and MS switching fabric. Similar models have been introduced for the asynchronous case (Eramo et al., 2009c; Eramo, 2010) and when the SPW sharing strategy is adopted (Akar et al., 2011; Eramo et al., 2011). Some numerical results reporting the power consumption of Optical Packet Switches are illustrated in Section 4.3.

### **4.1 SOA's power consumption model**

The SOA's power consumption model illustrated in (Hinton et al., 2008) is adopted; the SOA's power consumption equals the supply power *Pal*,*<sup>G</sup> SOA* of the SOA needed to provide the gain *G*. *Pal*,*<sup>G</sup> SOA* can be expressed as follows:

$$P\_{SOA}^{dl,G} = V\_b i\_b = V\_b \left( 1 + \frac{\ln G}{\Gamma\_{SOA} \mathfrak{A}\_{SOA} L\_{SOA}} \right) i\_l \tag{1}$$

where *Vb* is the SOA forward bias voltage, *ib* is the polarization current, Γ*SOA* is the confinement factor, *αSOA* is the material loss, *LSOA* is the length and *it* is the transparency current given by:

$$i\_t = \frac{qw\_{SOA}d\_{SOA}L\_{SOA}N\_0}{\tau} \tag{2}$$

where *wSOA* is the SOA active region effective width, *dSOA* is the active region depth, *q* = 1.6 <sup>×</sup> <sup>10</sup>−9*<sup>C</sup>* is the electronic charge, *<sup>N</sup>*<sup>0</sup> is the conduction band carrier density required for transparency, *τ* is the carrier spontaneous decay lifetime.

### **4.2 Analytical models**

The analytical evaluation of the OPS power consumption is carried out as a function of the main switch and traffic parameters (Eramo, 2010; Eramo et al., 2011). We propose two analytical models to evaluate the power consumption of synchronous Optical Packet Switches equipped with Single-Stage and BENES switching fabric in Sections 4.2.1 and 4.2.2 respectively.
