TY - JOUR
T1 - Continuous-phase frequency-shift keying with external modulation
AU - Sakamoto, Takahide
AU - Kawanishi, Tetsuya
AU - Izutsu, Masayuki
N1 - Funding Information:
Manuscript received August 16, 2005; revised March 17, 2006. This work was supported in part by the 2004 Industrial Technology Research Grant Program from The New Energy and Industrial Technology Development Organization (NEDO) of Japan, and in part by the Ministry of Education, Culture, Sports, Science and Technology, under a Grant-in-Aid for Scientific Research.
PY - 2006/7
Y1 - 2006/7
N2 - A high-speed external modulation scheme for optical continuous-phase frequency-shift keying (CPFSK) is presented. In external frequency-shift keying (FSK) modulation using singlesideband modulation technology, an optical upper/lower sideband (USB/LSB) component with respect to a carrier frequency is selectively generated. However, the FSK-modulated signal has phase discontinuities at the timings of frequency shifts. To overcome the problem, we propose a synchronous control technique that enables continuous phase modulation. In the external CPFSK modulation, the USB/LSB is allowed to shift to the other state when their phases coincide with each other. It is shown that CPFSK with a zero-topeak frequency deviation of 0.5 × (bit rate) is achieved with this synchronous control. Occupant bandwidth is less than half that of the externally modulated incoherent FSK with phase discontinuities. At a modulation speed of 10 Gb/s, higher order sidelobes are highly suppressed by more than 20 dB at the 20-GHz offset, comparing to a conventional binary phase-shift keying (BPSK). By the use of a Mach-Zehnder interferometer with balanced photodetection, receiver sensitivity is 3-dB greater than that of an on-off keying, as well as a BPSK. In this paper, we report on the experimental demonstration of CPFSK modulation/demodulation. A six-channel wavelength-division-multiplexed, 10-Gb/s CPFSK modulation/demodulation was successfully demonstrated.
AB - A high-speed external modulation scheme for optical continuous-phase frequency-shift keying (CPFSK) is presented. In external frequency-shift keying (FSK) modulation using singlesideband modulation technology, an optical upper/lower sideband (USB/LSB) component with respect to a carrier frequency is selectively generated. However, the FSK-modulated signal has phase discontinuities at the timings of frequency shifts. To overcome the problem, we propose a synchronous control technique that enables continuous phase modulation. In the external CPFSK modulation, the USB/LSB is allowed to shift to the other state when their phases coincide with each other. It is shown that CPFSK with a zero-topeak frequency deviation of 0.5 × (bit rate) is achieved with this synchronous control. Occupant bandwidth is less than half that of the externally modulated incoherent FSK with phase discontinuities. At a modulation speed of 10 Gb/s, higher order sidelobes are highly suppressed by more than 20 dB at the 20-GHz offset, comparing to a conventional binary phase-shift keying (BPSK). By the use of a Mach-Zehnder interferometer with balanced photodetection, receiver sensitivity is 3-dB greater than that of an on-off keying, as well as a BPSK. In this paper, we report on the experimental demonstration of CPFSK modulation/demodulation. A six-channel wavelength-division-multiplexed, 10-Gb/s CPFSK modulation/demodulation was successfully demonstrated.
KW - Continuous-phase frequency-shift keying (CPFSK)
KW - External modulation
KW - Modulation formats
KW - Optical fiber communication
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U2 - 10.1109/JSTQE.2006.876181
DO - 10.1109/JSTQE.2006.876181
M3 - Article
AN - SCOPUS:33747313185
VL - 12
SP - 589
EP - 594
JO - IEEE Journal of Selected Topics in Quantum Electronics
JF - IEEE Journal of Selected Topics in Quantum Electronics
SN - 1077-260X
IS - 4
M1 - 1668100
ER -