Impact of Carrier Contribution Factor in the Self-Coherent DC-Value Method

The carrier contribution factor (CCF) is used in the DC-value method to assure the minimum phase condition (MPC) at the transmitter. We analyze the impact of the CCF estimation accuracy at the receiver on the DC-value system performance. We found that the CCF estimation accuracy at the receiver should be within ±5% to exploit all advantages of the DC-value method. We propose an accurate method to estimate the CCF at the receiver that works effectively with both direct current (DC) and alternating current (AC) coupled photodetectors. We experimentally validate the proposed method employing a 24 GBaud 16QAM signal. The experimental results show that the minimum BER value can be approached within ±5% offset of the estimated CCF value almost independently of the carrier to signal power ratio (CSPR) value. The proposed method can also be used to reconstruct the DC component in other minimum phase signal self-coherent techniques, such as the Kramers-Kronig receiver.