Optical phase conjugation technique using four-wave mixing in ...

electrical power, dBm
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
0
pump
conjugate
1 2 3 4 5 6 7 8 9
frequency, GHz
Fig. 2 Measured spectrum at optical receiver output for 500 MHz
modulation frequency
Horizontal co-ordinate represents frequency detuning between laser 2 and pump
and conjugate waves. This frequency is measured in gagahertz. Vertical coordinate
represents measured electrical power measured in dBm
We repeated this measurement for modulation frequencies ranging
from 0.5 to 3.5 GHz with 0.5 GHz steps. The conjugate signal power
(relative to its power at 500 MHz) is shown in Fig. 3. The frequency
response is not flat, as predicted in [1].
relative power, dB
0
–2
–4
–6
–8
–10
–12
–14
0.5
1.0 1.5 2.0
frequency, GHz
2.5 3.0 3.5
Fig. 3 Conjugate wave relative powers measured in dB
Reference power is 227 dBm. Modulation frequencies are 0.5, 1, 1.5, 2, 2.5, 3
and 3.5 GHz
Operation conditions are same as in Fig. 1
Conclusion: We have shown experimentally that, in strong contrast to
existing techniques, SOA-based optical conjugation schemes are not
necessarily restricted to the highly non-degenerate four-wave mixing
regime, because the probe and conjugate waves can propagate in opposite
directions inside the SOA, as proposed in [1].
Acknowledgments: This work was supported in part by the Spanish
Department of Education under the Programa Nacional de Movilidad
de Recursos Humanos del Plan Nacional de I + D + I 2008-2011 and
Science Foundation Ireland, Principle Investigator Award (09/IN.1/
II2641).
# The Institution of Engineering and Technology 2011
22 March 2011
doi: 10.1049/el.2011.0737
One or more of the Figures in this Letter are available in colour online.
C.L. Janer (Departamento de Ingenieria Electronica, Escuela Superior
de Ingenieros, Universidad de Sevilla, Seville, Spain)
E-mail: janer@us.es
M.J. Connelly (Optical Communications Research Group, Department
of Electronic and Computing Engineering, University of Limerick,
Limerick, Ireland)
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ELECTRONICS LETTERS 9th June 2011 Vol. 47 No. 12