Beyond 25 Gbit/s Directly Modulated, Directly Detected OFDM Using Channel Flattening by a Fabry-Perot Filter

Abstract

We experimentally demonstrate the joint use of OFDM and channel flattening effect provided by a Fabry-Perot filter to allow higher than 25 Gbit/s direct intensity modulated, directly detected transmission over up to 75 km SSMF.

DAC-less and DSP-free 20 Gb/s PAM-4 transmission based on a dual modulation scheme using DML and external modulation

“…In the reference case after 75-km we observe a time skew on the eye diagram which is linked to chromatic dispersion effect also explaining the impossibility to measure any BER. In the case of dual modulation, the time skew is less present thanks to the combination of laser chirp and shifted optical filter as observed in previous work [11].…”

“…We can see on Fig.8, the eye diagrams associated to dual modulation and PAM-4 reference after 25, 50 and 75-km.In the reference case after 75-km we observe a time skew on the eye diagram which is linked to chromatic dispersion effect also explaining the impossibility to measure any BER. In the case of dual modulation, the time skew is less present thanks to the combination of laser chirp and shifted optical filter as observed in previous work[11].4. ConclusionsWe demonstrate experimentally the use of a dual modulation scheme, using direct laser modulation and external modulation, to generated a DAC-less, DSP-free, 20 Gb/s PAM 4 signal.…”

“…Two pulse pattern generators (PPG1 and PPG2) are used to generate two 10 Gb/s electrical signal with delayed patterns of pseudorandom binary sequence of length 2 15 -1. The LM-EML is emulated by a DML with an E/O bandwidth of 15 GHz [11] followed by a LiNbO3 Mach-Zehnder modulator (MZM). A Fabry-Pérot filter with a slope of 1 dB/GHz is used to improve the DML extinction ratio and dispersion tolerance as proposed in [11].…”

“…The LM-EML is emulated by a DML with an E/O bandwidth of 15 GHz [11] followed by a LiNbO3 Mach-Zehnder modulator (MZM). A Fabry-Pérot filter with a slope of 1 dB/GHz is used to improve the DML extinction ratio and dispersion tolerance as proposed in [11]. An erbium-doped fiber amplifier (EDFA) was placed after the filter to preamplify before transmission through a standard single-mode fiber (SSMF).…”