Abstract
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.
| Original language | English |
|---|---|
| Article number | 1668100 |
| Pages (from-to) | 589-594 |
| Number of pages | 6 |
| Journal | IEEE Journal on Selected Topics in Quantum Electronics |
| Volume | 12 |
| Issue number | 4 |
| DOIs | |
| Publication status | Published - 2006 Jul 1 |
| Externally published | Yes |
Keywords
- Continuous-phase frequency-shift keying (CPFSK)
- External modulation
- Modulation formats
- Optical fiber communication
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics
- Electrical and Electronic Engineering