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We report 108 Gb/s Duo-Binary PAM-8 (DB-PAM-8) transmission using direct-detection aided by Volterra equalizer. The bit-error-rate (BER) performance of the DB-PAM-8 signal has been evaluated through error counting by varying the bit rate, received optical power, and reach. The experimental results suggest that up to 108, 102, and 84 Gb/s signals can be propagated in back-to-back (B2B), and over 10, and 20 km of standard single-mode fiber (SMF), respectively, below the low-density parity-check forward error correction (LDPC-FEC) threshold. Furthermore, we derive a probabilistic model of the BER for multilevel DB-PAM-M signaling that is verified using our measurements. The model of this important performance metric turned out to be accurate enough, especially at low BER values, where its use is more convenient. [ABSTRACT FROM AUTHOR]

We demonstrate 100 Gb/s/ $\lambda $ duo-binary PAM-4 (DB-PAM-4) transmission over 50 km standard single-mode fiber (SMF) in the O-band using a 20G silicon-based transmitter and a 25G optically-amplified PIN+TIA-based receiver for 100G PON downstream applications. Receiver sensitivities of −15, −14.5 and −12 dBm are achieved at a bit error rate (BER) below the low-density parity-check forward error correction (LDPC-FEC) threshold (i.e., $1\times 10^{-2}$) in back-to-back (B2B), and after 20 and 50 km, respectively using a 131-tap linear feed-forward equalizer (FFE) at the receiver. According to the results, a power budget of 20 dB can be achieved for 20 km transmission. Furthermore, we report the performance of 99 Gb/s (33 Gbaud) PAM-8 transmission and show that DB-PAM-4 provides 5.3 dB better sensitivity compared to PAM-8 at the LDPC-FEC threshold. [ABSTRACT FROM AUTHOR]

We demonstrate 25 and 50 Gb/s four-level pulse amplitude modulation (PAM-4) transmission over 43- and 21-km standard single-mode fiber (SMF), respectively, using a silicon photonic 120° hybrid-based integrated simplified coherent receiver in the $C$ -band. The integrated receiver is composed of an edge coupler, a vertical grating coupler, a polarization splitter–rotator, a $3\times 3$ multimode interference coupler-based 120° hybrid, and three germanium p-i-n photodetectors. For 25 Gb/s PAM-4 transmission, we achieved the receiver sensitivities of −18, −17.5, −16.6, −14.5, and −9.8 dBm in back-to-back (B2B) and after 10.5, 21, 31, and 43 km, respectively, at a bit error rate (BER) below the hard-decision forward error correction (HD-FEC) threshold (i.e., $3.8\times 10^{-3}$) without using any receiver equalizer, while for the 50 Gb/s PAM-4 transmission, the receiver sensitivities of −13.6 dBm in B2B, and −13.5 and −11.6 dBm after 10.5 and 21 km are obtained using a 31-tap linear feed-forward equalizer (FFE), respectively. Furthermore, we achieved up to 44 Gb/s receiver equalizer-free PAM-4 transmission over 10.5 km below the HD-FEC. The characterization of the receiver at different wavelengths within the $C$ -band is provided as well. [ABSTRACT FROM AUTHOR]

A packaged silicon photonic traveling wave Mach–Zehnder modulator operating at 1310 nm is presented and studied. The modulator is a series push–pull device and requires a bias applied to the common n-doped region. Effects of varying the bias voltage on the modulator's V\pi , bandwidth, and on chip-insertion loss are studied, and its impact on transmission performance are experimentally investigated for PAM-4 and PAM-8 formats at a throughput of 112 Gb/s, over varying distances of 0, 2, 10, and 20 km. Residual chromatic dispersion is shown to have no impact on performance up to 20 km. The PAM RF driving waveform is generated by an 8-bit digital-to-analog converter, while direct detection is done with a PIN+TIA followed by an 8-bit analog-to-digital converter. This IM/DD system utilizes digital signal processing with transmitter spectral compensation and receiver residual equalization. The performance impact for a varying number of transmitter precompensation taps and receiver equalization taps is studied, which has a direct impact on the transceiver's power consumption. Using PAM-4, a BER below the FEC limit is obtained for either combinations of (transmitter, receiver) tap lengths: (19,19), (7,27), or (35,7), allowing flexibility in power consumption distribution. [ABSTRACT FROM PUBLISHER]

Providing a low-cost, reliable and end-to-end quality of service (QoS) guaranteed connectivity is going to be a major challenge in optical transport due to the immense growth in number of connected devices and traffic volume triggered by fifth-generation mobile networks (5G) and cloud networks. First, we discuss the architectures of the 5G transport network and the data center network, to capture the full value of connectivity. The paper offers an overview of the network requirements and how the integrated photonic platforms, along with the advanced modulation formats, play a key role to support the unprecedented requirements of 5G and massive cloud deployment. Second, we provide an overview of the recent work on the development of high-speed silicon photonic (SiPh) modulators to generate and transport PAM-4 signals. Third, recent advancements of the photodetectors, optical hybrids, and integrated coherent receivers on the silicon-on-insulator (SOI) platform are also described. The results suggest that, in the first access and aggregation segments of the network, integrated silicon-based modulators aided by PAM-4 modulation formats can support the stringent requirements of new generation transport networks in terms of speed, footprint and power consumption. [ABSTRACT FROM AUTHOR]