Pablo Torres-Ferrera

Design and Technical Feasibility of Next 400 GbE 40-km PMD Based on 16

The technical feasibility of a straightforward and cost-effective extension of the current 100 Gb/s Ethernet 40-km physical medium dependent (PMD) architecture for single-mode fiber to a higher speed of 400 Gb/s is demonstrated by means of simulations. A 16-wavelength configuration, each running at 25 Gb/s in non-return-to-zero modulation format and using plain direct detection is numerically analyzed and optimized. It is shown that error-free performance is achievable when a channel plan slightly shifted from the zero-dispersion wavelength of the transmission fiber and having a channel spacing of 400 GHz is utilized. However, to meet the power budget requirement in a fiber having an attenuation coefficient of 0.50 dB/km, a semiconductor optical pre-amplifier with a small-signal gain of 23 dB and transmitters having a minimum average output power of +2.9 dBm and an extinction ratio of 8 dB have to be employed. Based on the calculated design margins, the use of flexible active devices is suggested for span lengths shorter than 40 km.

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The proposal and technical feasibility of a wavelength-division multiplexed system consisting of eight optical channels, each transporting data at 50Gb/s in NRZ modulation format, are presented. It is numerically demonstrated that, aided by a semiconductor optical pre-amplifier with 23dB of gain and setting the laser output power of an electro-absorption-based transmitter to +7.9dBm, a propagation distance of 40km over conventional single-mode optical fiber can be achieved with a BER < 1×10-13. Despite its high sensitivity, dispersion power penalty is minimized by setting a 400GHz channel plan in O-band whose center is slightly red-shifted from the zero-dispersion wavelength of the fiber. Moreover, non-zero dispersion is found to be useful in reducing the deleterious amplifier nonlinear gain modulation at mid-range distances, whereas four-wave mixing is found to play a practically inconsequential role. In agreement with previous results derived for 25Gb/s multi-channel links, optical signal-to-noise ratio degradation becomes the prominent corrupting factor at long fiber span lengths. The proposed architecture thus represents an alternative for the implementation of the physical layer of next-generation Ethernet or similar metropolitan data networks.

25 Gbps Architecture

A cascade of two-stage coarse and fine WSS is studied for Nyquist- and quasi-Nyquist WDM systems. Results show that edge tributaries experience excess performance degradation, resulting in a transmission distance drop by about a factor of 2 for quasi-Nyquist WDM.

An alternative for the implementation of 40-km reach Ethernet at 400Gb/s using an 8Ö50Gb/s PHY at 1310nm with SOA pre-amplification

Technical feasibility of a 10km, 100Gbps, single-optical channel transmission-system based on direct-detection OFDM that does not require amplification or FEC is numerically demonstrated for BER<10E-12. This is a cost-effective alternative for next-generation 100 Gbps Ethernet.

Filtering effects of cascaded flex-grid roadms with high spectral resolution filters on the transmission of Nyquist and quasi-Nyquist WDM super-channels

An eight-channel multi-format coherent optical transceiver is proposed as an alternative to implement terabit metro inter-data centre interconnects (DCI) transmitting from 800 to 1600 Gb/s over conventional single mode fibre (CSMF). The maximum reach of the system as a function of transmitted power and overall capacity is numerically estimated for a BER target of 1×10−13, avoiding the use of optical amplification and FEC schemes. A maximum reach of 114, 81 and 40 km is found for data rates of 800, 1200 and 1600 Gb/s when QPSK, 8PSK and 16-QAM are set as modulation formats, respectively, and the optical power at the lasers output is set to 13 dBm. No relevant transmission power penalties are found for the analysed systems because they are fully compensated by electronic digital signal processing at the receiver. This is not the case for other noise sources generated at the transceivers. Additionally, moderate OSNR penalties due to fibre attenuation, that increase as the modulation format order increases and as the BER target decreases, are calculated.

Unamplified 10-km transmission using direct-detection optical OFDM superchannel at 100 Gbps

The technical feasibility of an unamplified 4 × 100 Gb/s wavelength division multiplexed direct-detection optical OFDM system that uses electro-absorption modulators (EAM) as transmitters is numerically demonstrated for up to 10-km reach of single-mode fiber (SMF) in O-band and 800 GHz-channel spacing. Based on the use of currently available optical components, most of which were developed for the current long-reach Ethernet standard, operating around 1300 nm, error-free operation (pre-FEC BER <; 3.8E-5) is achieved. The architecture here put forward represents a backward compatibility alternative that can be used to define next-generation 2- and 10-km 400 Gb/s Ethernet standard.

Multi-format 800 – 1600 Gb/s coherent transceiver for inter-data centre interconnects over SMF

The nonlinear response of a bulk semiconductor optical pre-amplifier in a 16 × 25 Gb/s WDM implementation for the next 40-km Ethernet link, operating at 400 Gbps is numerically analysed. It is found that the effect of carrier-heating-induced four-wave mixing for channel spacing values between 200 and 800 GHz is rather modest despite the large number of optical channels. In contrast, cross-gain modulation is uncovered as the main impairment, and its dependence on the system channel-spacing value is quantified and explained in terms of the interplay between amplifier saturation and fibre dispersion. Useful design parameters for the optoelectronic transceivers, operating at 25.781 Gb/s in traditional on-off keying scheme, are put forward.

Next-generation 400 Gb/s Ethernet PMD over SMF at 1310 nm via DD-OFDM with electro-absorption modulator-based transmitters

Technical feasibility of 10x40 and 8x50 Gbps 10-km pre-amplified systems is demonstrated for BER≤1E-13 with channel spacing of 800GHz and a minimum laser power of +7.7dBm. The latter system is recommended for implementing 400 GbE