## 3 Experimental Demonstration
### Experimental Results
Clearly optimizing the position of the pump wavelengths (left/right of input and/or output signals) could lead to further improvement, while requiring slightly more pump wavelengths. Previous studies [8,10] demonstrated conversion efficiency below \(-\)8 dB: \(-\)10 dB for OOK and \(-\)11.5 dB for DPSK in [10] and \(-\)8 dB in [8]. Pump powers were high, 7 dBm in [8] and \(P_{P_{1}}=~{}10.5\) dBm and \(P_{P_{2}}=6.5\) dBm for OOK and \(P_{P_{1}}=11\) dBm and \(P_{P_{2}}=7\) dBm for DPSK in [10]. We achieve higher conversion efficiency (\(-\)3.6 dB in average for OOK and \(-\)5.4 dB for DPSK) with an OSNR of \(\sim\)31.3 dB/0.1 nm for OOK and \(\sim\)32.1 dB/0.1 nm for DPSK on average at pump powers below 1 dBm. The improvement is most likely due to the smaller detuning between the signal and first pump in our experiments. In [10] a detuning of 6.6 nm was used in order to achieve polarization independence, but at the cost of a bit error floor and extremely limited tuning range. In [8] the detuning was 1.6 nm, but a different SOA was used and operating points were chosen to optimize performance in a cascade of 10 wavelength conversions; tuning range was not examined and only a single pump was used. The conversion efficiency for 48 separate experiments over 12 nm tuning range is reported in Table 1 for OOK and DPSK. We consider 16 wavelengths for OOK (\(\lambda_{Sig}\) = 1549 nm for original signal and \(\lambda_{WC}\) from 1549.8 nm to 1561 nm for the converted signals) and for DPSK (\(\lambda_{Sig}\) = 1548.5 nm for original signal and \(\lambda_{WC}\) from 1550.1 nm to 1561.3 nm for the converted signals). The conversion efficiency for the converted signals shown in Figure 3a is reported in the first row of Table 1. From the first row of Table 1, the conversion efficiency fluctuates by 1.3 dB for OOK and 1.2 dB for DPSK with best case: \(-\)3.1 dB for OOK and \(-\)4.9 dB for DPSK; and worst case: \(-\)4.4 dB for OOK and \(-\)6.1 dB for DPSK. We have an average conversion efficiency of \(-\)3.5 dB for OOK (and \(-\)5.6 dB for DPSK) for \(\lambda_{8}\) and \(-\)3.8 dB for OOK (and \(-\)5.7 dB for DPSK) for \(\lambda_{16}\), we expect that approximate values are achievable for the other wavelengths. For the 48 performed measurements, we achieve high conversion efficiency with an average value of \(-\)3.6 dB for OOK and \(-\)5.6 dB for DPSK. The maximum/minimum values for CE are \(-\)2.6/\(-\)4.9 dB and \(-\)5.1/\(-\)6.7 dB, for OOK and DPSK, respectively. The standard deviation is 0.2 dB for both OOK and DPSK. We notice that the values for conversion efficiency do not degrade with a wider conversion range. Using 16 pump wavelengths, we could theoretically cover an even wider tuning range (12 nm) to achieve 240 conversions over 16 channels. The conversion efficiency dependson the detuning values between the signal and the closest pump as demonstrated in [12]. Therefore, the conversion efficiency value for DPSK is lower than for OOK because the detuning between the signal and the closest pump is larger for DPSK. BER measurements are performed over a 12 nm conversion range covering 16 channels with 100 GHz spacing as shown in Figure 4. Results for BER _vs._ received optical power (measured at point D of Figure 2) are presented in Figure 5, with OOK reported in Figure 5a and DPSK in Figure 5b. Due to the copolarized dual pump configuration, the system is optimized for each converted wavelength using the polarization controllers to maximize the pump alignment. The power penalty at BER of \(10^{-9}\) is used as a measure of the system performance degradation by the wavelength conversion process. Moderate power penalty is measured as the original signal is successively converted into the 16 new wavelengths for both OOK and DPSK (lower than 2 dB for OOK and lower than 3 dB for DPSK). Comparing Figure 4a with BER results, we see the same trends from conversion efficiency repeated in the BER results.