Direct Phase Modulation DFBs for Cost-Effective ONU Transmitter in udWDM PONs

DQPSK Directly Phase Modulated DFB for Flexible Coherent UDWDM-PONs

“…Initially, the channel spacing between ONUs in upstream was set at 12.5 GHz. The Tx electrical signal amplitude was tuned to get the desired phase changes and diminish the residual amplitude modulation (AM res ) as in [5]. The results of BER against the OLT Rx optical input power are plotted in Fig.…”

“…2). External modulation with a dual mach-zehnder modulator (MZM) would diminish the AM res and improve the performance by at least 2dB as with DPSK format [5]. ONU 2 laser wavelength was then tuned for evaluating the minimal spectral separation needed.…”

“…In [4], an optical differential phase shift keying (DPSK) modulation of a distributed feedback (DFB) laser was reported with direct detection. Similarly, in [5] a direct phase modulated DFB with DPSK data was proposed for optical network unit (ONU) Tx and detected with a heterodyne receiver (Rx).…”

“…Then they directly modulate two equalized DFB lasers (λ 1 =1549.3nm and λ 2 =1549.4nm). The high pass equalization (based on an RC network), in the DFBs converted the adiabatic frequency modulation into phase modulation [5]. The result was a signal with either 0º and 180º variations (DPSK) or 0º, 90º, 180º, 270º phases (DQPSK).…”

1Gbps full-duplex links for ultra-dense-WDM 625GHz frequency slots in optical metro-access networks

“…The transmitted symbols in the OLT Digital Transmitter (DTX Di ) are filtered using a Nyquist Pulse Shaper filter with 12-symbols filter length and zero roll-off factor. The transmitted symbols generated in the ONU Digital Transmitter (DTX Ui ) are bipolar Non Return to Zero (NRZ) coded and high-pass filtered to obtain the phase modulation of the laser [7,10]. The DTX are implemented in MATLAB TM and the electrical signals are generated by a 12GSa/s Arbitrary Waveform Generator.…”