Here is link of one paper that may help you you may refer to it.
http://ieeexplore.ieee.org/xpl/articleDetails.jsparnumber=6334404&newsearch=true&queryText=Constant%20Envelop%20MinimumShift%20Keying%20OFDM%20Coherent%20Optical%20Communication%20System
In this paper, we propose a constant envelop minimum-shift keying orthogonal frequency division multiplexing (CE-MSK-OFDM) modulation scheme. This scheme can mitigate the inherent drawbacks of CE quadrature phase shift keying OFDM (CE-QPSK-OFDM) and MSK-OFDM. Advantages of the proposed CE-MSK-OFDM modulation scheme are theoretically investigated. A CE-MSK-OFDM coherent optical experimental system is presented. In our experiment, 2.5 Gb/s CE-MSK-OFDM signal and 2.5 Gb/s CE-QPSK-OFDM signal are transmitted over a 100 km standard single mode fiber (SSMF) without phase compensation to check its advantages in mitigating intercarrier interference (ICI). In addition, performance under large fiber launch power is also measured to check its advantages in counteracting fiber nonlinear impairments. The experimental results show that the proposed system performs well in decreasing ICI and peak-to-average power ratio (PAPR) as the theoretical analysis reveals.
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