1.25–3.125 Gb/s per user PON with RSOA as phase modulator for statistical wavelength ONU

Abstract

a b s t r a c tWe report a new scheme to support, cost efficiently, ultra-dense wavelength division multiplexing (UDWDM) for optical access networks. As validating experiment, we apply phase modulation of a reflective semiconductor optical amplifier (RSOA) at the ONU with a single DFB, and simplified coherent receiver at OLT for upstream. We extend the limited 3-dB modulation bandwidth of available uncooled To-can packaged RSOA ( $400 MHz) and operate it at 3.125 Gb/s with the optimal performance for phase modulation using small and large signal measurement characteristics. The optimal condition is selected at input power of 0 dB m, with 70 mA bias condition. The sensitivities at 3.125 Gb/s (at BER¼ 10 À 3 ) for heterodyne and intrady Q2 ne detection reach À 34.3 dB m and À 38.8 dB m, respectively.

Field-Trial of a High-Budget, Filterless, $\lambda$ -to-the-User, UDWDM-PON Enabled by an Innovative Class of Low-Cost Coherent Transceivers

“…At the ONU side, the receiver consisted in a polarization independent heterodyne mixer [26]. The ONU front-end used a network of optical circulator and 3 dB couplers/splitters separating US/DS traffic and allowing to use a single DFB laser (DFB-3 in Figure 6) simultaneously as LO and seed for the upstream Reflective Semiconductor Optical Amplifier (R-SOA) transmitter [34] [35]. The LO emission frequency was shifted by +2.5 GHz from the receiving signal and its power was set to 0 dBm.…”

“…The US transmitter used a directly-modulated TO-CAN R-SOA, biased at 70 mA with 18 dB linear gain although here under saturation for phase modulation, and was coupled to the ODN with 3 dBm optical power. At the OLT, the US signal was detected by a polarization dependent coherent heterodyne receiver with another DFB laser (DFB-2) as LO, which implemented the same analogue processing described above but using balanced detection [34]. 1.25 Gb/s homodyne PSK system was also implemented by using directly phase-modulated DFB lasers (see Figure 7).…”

Coherent ONU based on 850 μm-long cavity-RSOA for next-generation ultra-dense access network

“…Furthermore, extending the number of accommodated users requires UDWDM solutions, with the purpose of opening the way to the "wavelength-to-the-user" concept and providing the independent bit rate [2] . With the goal of implementing UDWDM-PONs for the end user, the lowfootprint integrated RSOA can be efficiently modulated and coherently detected for the configuration of the access network [8][9][10][11][12] .…”

“…Considering the power budget, there is a solution to employ coherent detection and an integrated laser (low footprint) at the ONU to highly enhance the sensitivity and the total bandwidth (BW). At the same time, the phase modulation of the RSOA at the ONU is an advantageous approach for long-reach UDWDM-PONs [9][10][11] .…”

“…An RSOA chip has been implemented with a relatively low optical confinement factor (Γ ¼ 20%) and a relatively long active section (L ¼ 850 μm), which appears to be optimum for this application [10,11,15] . The RSOA has a polarization-independent chip structure, which is discussed in detail in Refs.…”