We demonstrate first simultaneous bidirectional operation of coherent point-to-point overlay over PON ODN delivering 400G at 29-dB and 200G/100G at > 35-dB optical budget using off-the-shelf pluggable single-laser single-carrier coherent transceivers. We propose to use duplex feeder to overcome limitations due to distributed Rayleigh backscatter. (c) 2025 The Author(s)

Analog multiplexer (AMUX) integrated circuits (ICs) expand the analog electrical bandwidth of transmitter frontends, enabling signal generation at ultrahigh symbol rates. In this work, we employ a SiGe AMUX which adopts a circuit topology optimized for signal linearity, supporting high-order modulation formats, such as multilevel pulse amplitude modulation (PAM). We discuss in detail the circuit design of the AMUX, including its AMUX core, clock path and output amplifier. We compare two circuit topologies with respect to power consumption, circuit complexity, clock strength and inputto-output linearity. We also perform theoretical analysis of signal impairments induced by misalignments between AMUX inputs to understand their impact on the integrity of the interleaved signal. Using this high-performance SiGe AMUX to drive an optical intensity modulator, we experimentally demonstrate generation and 2 km fiber transmission of different orders of PAM, up to PAM-8 at 176 GBd yielding a net bitrate of 467 Gbit/s.

We experimentally demonstrate a bidirectional, cross-gain-modulation-free, bismuth-doped fiber amplifier (BDFA) for O-band high-speed passive optical networks. Based on the spatially and spectrally resolved gain profiles of the bidirectional BDFA characterized via Rayleigh backscattering measured by a coherent swept wavelength interferometer, an optimization scheme for bidirectonal amplification is introduced. The BDFA is located at the optical line terminal and acts as both a downstream (DS) signal booster and a pre-amplifier for the upstream (US) burst mode signal, with an equal bidirectional saturated gain of 21.3 dB and noise figure of 5.7 dB, which offers 20.8-dB DS and 17-dB US power budget improvement. Our experimental results also indicate that the transient impact of the BDFA is negligible, as it is saturated by the DS signal, resulting in an US power budget penalty of only 0.5 dB in burst mode.

Co-packaging of optics and electronics is essential to alleviating scaling bottlenecks in short-reach high-bandwidth applications such as datacenter links and interconnections. One transmit- side solution includes a shared WDM or gray optics laser source and dense arrays of high-speed, low power consumption modulators. With this in mind, we have demonstrated high-speed NRZ and PAM-4 direct detection links based on surface normal electro-absorption modulators (SNEAMs). SNEAMs are particularly attractive for co-packaged optics and other short-reach applications due to their low power consumption, high-speed, polarization independence, wide operating wavelength band, and small footprint. Here we describe short-reach transmission studies of SNEAMs at baud rates up to 80 Gbaud (160 Gbps PAM-4) and over optical bands spanning up to 32 nm. We show the potential for dense modulator arrays with a proof-of-concept experiment that integrates a 4-channel array of SNEAMs with a 4-channel array of electronic drivers. We also report a demonstration of SNEAMs as remote modulators in a centrally-sourced WDM passive optical network.

We first characterize the spatially and spectrally resolved gain profiles of an O-band BDFA via Rayleigh backscattering measured by a coherent swept wavelength interferometer, with a small signal gain reaching 35 dB at 1320 nm.

We experimentally show feasibility of downstream 200 Gbit/s IM/DD TPDM PON system with >4 dB margin to 29 dB optical power budget based on two 100 Gbit/s polarization channels in a single wavelength window. The system uses SBS suppression to mitigate nonlinear fiber loss and duoternary modulation to overcome bandwidth limitation.

Using a SiGe analog multiplexer (AMUX) integrated circuit we generate a PAM-8 signal at 176 GBd by time-interleaving two 88 GBd tributaries. High-quality signal is obtained after interleaving thanks to the excellent linearity of the AMUX. We successfully demonstrate net bitrates up to 467 Gbit/s after 2 km fiber transmission.

Short-reach communication systems use electro-optic transmission engines based on low-voltage, wide bandwidth modulators to achieve high capacity and low power operation. Here, we demonstrate, for the first time, integration of a 4-channel array of surface-normal electroabsorption modulators (SNEAMs) with a 4-channel array of electronic drivers with low output voltage (~1.25-1.45 Vpp). We use this 4-channel SNEAM-driver array electro-optic engine to demonstrate $4 \times 53$ Gbit/s non-return-to-zero on-off-keying transmission across up to 2 km of standard single mode fiber over a broad wavelength range (about 26 nm), the widest band of operation achieved with SNEAMs. Integration of a SNEAM array with a low output voltage driver array, a result that we achieved thanks to the use of SNEAMs that operate with low voltage swings, represents a fundamental milestone toward the realization of optical modules based on SNEAMs.

We demonstrate a WDM passive optical network that uses high-speed, polarization-independent surface normal modulators as upstream 25-Gb/s transmitters. A band of CW wavelengths, sourced at the optical line terminal, establishes the upstream channels. System performance in our single-fiber architecture is limited by Rayleigh backscattering, but is below the FEC threshold.

Comb sources and multi-wavelength lasers can be used as central sources of light in many communication systems using high channel count wavelength division multiplexing. Here, we demonstrate a 16 wavelengths comb source built through large scale hybrid integration of 16 active gain chips with a passive silica chip that incorporates a 16 channel arrayed waveguide grating. Optical coupling between the 16 gain chips and the silica chip is achieved through 32 ball lenses (two per channel), that are aligned and attached in place with an automated process that we developed. The 16 channels have 100 GHz spacing and are centered in the C-band. We show monomode lasing, both in single-channel and multi-channel operation, with side mode suppression ratio as high as, respectively, 67 dB and 55 dB. The total output power of our comb source is about 17.9 dBm when all the 16 channels are activated simultaneously. The channels of our multi-wavelength laser have very narrow Lorentzian linewidths, with best value as narrow as 880 Hz and worst value of about 3.6 kHz. Our comb source integrates hybridly a large number of optical components, however thanks to the parallel architecture and the possibility of packaging the lenses with an automated process, our integration approach can be scaled to an even higher number of channels.

We demonstrate the first 200-Gb/s (100-GBaud PAM-4) TDM-PON using directly modulated lasers and direct detection. We achieve >29-dB link power budget by combining distributed Raman amplification over 21-km fiber and an SOA-based pre-amplifier.

Colleagues pay tribute to Jane M. Simmons, Editor-in-Chief of the Journal of Optical Communications and Networking , who passed unexpectedly on 25 August 2021.

We demonstrate a direct-modulation and direct-detection system with a back-to-back line rate of 411.6 (net bit rate of 337.5) Gb/s using a 65 GHz DFB+R laser. The O-band laser with a chirp parameter of 0.6 supports dispersion-tolerant transmissions up to 15 km without an optical amplifier.

We measure performance of 44-Gb/s (22-GBd) PAM-4 short-reach direct detection links with a polarization-independent surface-normal electro-absorption modulator. Performance below the KP-4 FEC threshold is demonstrated in standard single-mode fiber links with no dispersion compensation for distances up to 18 km.

We report multi-level modulation in polarization-independent surface-normal electro-absorption modulators (SNEAMs). Four-level pulse amplitude modulation (PAM-4) at a line rate of 44 Gb/s is demonstrated on a fully packaged SNEAM with a 30 µm active area diameter and a 14 GHz electro-optic bandwidth. High-capacity PAM-4 transmission at 112 and 160 Gb/s is demonstrated on an unpackaged SNEAM chip, with a 15 µm active area diameter and ultrawide electro-optic bandwidth ( ≫ 65 G H z ). Fiber transmission is investigated for direct detection link lengths up to 23 km at 44 Gb/s and 2 km at 112 and 160 Gb/s, the highest multi-level modulation rates achieved on a SNEAM.

We study Raman Amplification for short-reach systems. The impact of system parameters, including feeder length and discrete losses are reported. Our measurements focus on the NG-PON2 upstream band, but are extensible to other optical bands, including O-band.

We use bi-directional distributed Raman amplification to offset the excess losses of an intelligent splitter module. We demonstrate this technique in a 42-km, 1: 32 split, TWDM PON.

The OFC 2017 Special Issue is a collection of outstanding optical networking papers based on OFC 2017 invited papers and the most highly ranked OFC contributed papers. The papers in this special issue cover a broad range of topics including elastic optical networks, open systems, machine learning, cross-layer optimization, and access networks.

We demonstrate an intelligent symmetric-rate 8- x 10-Gb/s bidirectional time and wavelength-division multiplexed passive optical network with 42-km reach and 1: 256 split 1425-nm laser pump light provides distributed Raman amplification for the upstream channels (allowing low-cost low-power transmitters), serves as a low-rate telemetry channel, and powers an intelligent splitter module that provides supervision for mission-critical services