An Economic Phase-Mdulation to Intensity-Modulation Converter
Open Access JCC
For Bessel function, the Jn is equal to -j-n when n is
odd. From (2), we can find that if the phase modulated
signal is directly injected into a PD, the center carrier
will individually beats with +1 and −1 sidebands, result-
ing in two electrical signals with the same amplitude, the
same frequency but different phase. So the PD will not
have any output signal. Nevertheless, when the phase-
modulated signal is injected into the proposed tunable
IM-to-PM converter, the optical intensity of the +1 side-
band will be boosted up. As shown in Figures 2 and 3,
the optical power variation between the +1 and −1 side-
bands is significantly promoted from 0 dB to 26 dB. A
clear eye diagram and obvious electronic spectrum are
shown proof in Figure 3. This means that the proposed
tunable PM-to-IM converter can successfully modify the
received phase-modulated signal back into intensity-
modula t ion form a t .
3. Conclusion
In this paper, a novel PM-to-IM converter is proposed
Figure 2. The optical spectrum of phase-modulated RF sig-
nal.
Figure 3. The optical spectrum of phase-modulated RF sig-
nal after passing though the PM-to-IM converter.
Figure 4. The measured 1.25 Gbps/10GHz downstream sig-
nal spectr um .
and experimentally demonstrate for optical phase-mod-
ulated RoF transport systems. Comparing with the pub-
lished PM-to-IM conversion schemes, which employ DI,
FBG, OBPF or dispersion devices to achieve this target,
the proposed scheme can economically and efficiently
convert a phase-modulated signal back into intensity-
modulated signal by a VCSEL. This is the first one to
achieve PM-to-IM conversion process by a VCSEL. The
feasibility of the propos al is experimentally d emonstr ated
with open eye diagrams when it is employed to convert
phase-modulated RF signal.
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