Bi-directional Ultra-dense Polarization-diverse OFDM/WDM PON with Laserless Colorless 1Gb/s ONUs Based on Si PICs and <417 MHz mixed-signal ICs

Flexible real-time transmitter at 10 Gbit/s for SCFDMA PONs focusing on low-cost ONUs

“…The data conversion boards are equipped with a high-speed 12-bit Maxim MAX5881 DAC and a small interfacing FPGA in order to extract the data from the GTX link and provide additional functionality for the reset and synchronization of the DACs. Due to throughput limitations of the inter-FPGA communication, using a Virtex-6 LX75 FPGA at the converter boards that feature only 8 GTX transceivers and the maximum specified GTX line rate of 6.25 Gbit/s, the OLT Tx measurements were performed at a slightly reduced sampling rate of 3.2 GSa/s compared to the OTONES scheme in [7] in order to maintain stability. For a proof-of-concept, the following measurements use a transmission frame structure of N sync = 16, N ref = 64, N data = 64. with a cyclic postfix length of 32 OLT Tx samples, i.e., an extension of the symbol length by 3.125%.…”

“…In optical access PON networks there are stringent constraints on the cost, complexity and power consumption in the Optical Network Units (the end-user terminals) requiring the utilization of relatively lowcost analog electrical components like filters, modulators and signal converters at the ONUs and the reduction of complexity of the digital implementation. The cost reduction aspects in the OTONES network [7] also apply to the photonic part of the network wherein dedicated lasers for upstream (US) communication are saved by transmitting a laser seed provided in the DS, which is used for the US modulation of data. A photonic integrated circuit (PIC) is introduced for both the efficient DS extraction and US modulation.…”

“…In the framework of the OTONES project, the OLT Tx presented in this article applies the basic bandwidth scheme published in [7]. Spectrally, two slices of W Slice = 12.5 GHz of bandwidth each are transmitted per optical wavelength.…”

“…In our system, the frequency behavior of the gain blocks used in the multipurpose up/downconversion circuitry impaired the recorded signal below 7 MHz strongly. Thus the D-slot transmit scheme presented in [7] is modified in an innovative way avoiding the 5 carriers per SG near DC, i.e., around 16.3 MHz, are omitted, the SG bandwidth is increased by the same small amount (see also [11]). This makes it necessary to discard one of the 10 SGs, reducing the maximum DS throughput by 10% to 11.25 Gbit/s at 16QAM (Fig.…”

Passive optical networks based on OFDM: Perspectives and experimental verifications

“…This common optical source could be either a unmodulated carrier for distributed from a central location (e.g. OLT) to the ONU [4,5] or the modulated DS carrier that is remodulated by each ONU [2,6]. Early approaches using individual wavelength for each ONU in US direction [7] are neglected here, since these concepts can hardly be further scaled with WDM.…”