Abstract
We first demonstrate delta-sigma digitization and coherent transmission of data over cable system interface specification (DOCSIS) 3.1 signals in a hybrid fiber coax (HFC) network. Twenty 192-MHz DOCSIS 3.1 channels with modulation up to 16384QAM are digitized by a low-pass cascade resonator feedback (CRFB) delta-sigma analog-to-digital converter (ADC) and transmitted over 80-km fiber using coherent single-λ 128-Gb/s dual-polarization (DP) quadrature phase-shift keying (QPSK) and 256-Gb/s DP-16QAM optical links. Both one-bit and two-bit delta-sigma digitization are implemented and supported by the QPSK and 16QAM coherent transmission systems, respectively. To facilitate its practical application in access networks, the coherent system is built using a low-cost narrow-band optical modulator and RF amplifiers. Modulation error ratio (MER) larger than 50 dB is successfully demonstrated for all 20 DOCSIS 3.1 channels, and high-order modulation up to 16384QAM is delivered over fiber for the first time in HFC networks. The raw DOCSIS data capacity is 54 Gb/s with net user information ~45 Gb/s. Moreover, the bit error ratio (BER) tolerance is evaluated by measuring the MER performance as BER increases. Negligible MER degradation is observed for BER up to 1.5 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> and 1.7 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> for one-bit and two-bit digitization, respectively.
Highlights
Video-intensive services, such as virtual reality and immersive applications are driving the growth of data traffic at user premises in an explosive way, making access networks become a bottleneck of user quality of experience
We first demonstrate the experimental results of DP-QPSK and DP-16QAM coherent transmission, and discuss the results of one-bit and two-bit digitization supported by QPSK/16QAM, respectively
We proposed and demonstrated delta-sigma digitization and coherent transmission of data over cable service interface specification (DOCSIS) 3.1 signals for the first time
Summary
Video-intensive services, such as virtual reality and immersive applications are driving the growth of data traffic at user premises in an explosive way, making access networks become a bottleneck of user quality of experience. In the United States, there are more than 50 million subscribers using cable services for broadband access, which is 40% more than digital subscriber line (DSL) and fiber-to-the-home (FTTH) users [10]. As a fifth-generation broadband access technology, DOCSIS 3.1 specifications are being commercialized at a historically rapid pace to support ultra-high-resolution videos (4 K/8 K), mobile backhaul/fronthaul (MBH/MFH), and other emerging applications enabled by virtual reality and internet of things [10,11,12,13,14]. With subcarrier spacing of 25 or 50 kHz, DOCSIS 3.1 specifications support downstream channel bandwidths 24–192 MHz, and upstream channel bandwidths 6.4–96 MHz [17,18,19]. Similar to the LTE carrier aggregation in MFH networks [20, 21], DOCSIS 3.1 specifications support channel bonding to designate more than one DOCSIS channels to a single user
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