Jose-Manuel Delgado Mendinueta

Advanced space division multiplexing technologies for optical networks [Invited]

Space division multiplexing (SDM) is mainly seen as a means to increase data throughput and handle exponential traffic growth in future optical networks. But its role is certainly more diverse. Research on SDM encourages device integration, brings newfunctionality to network elements, and helps optical networks to evolve. As a result, the number of individual components in future networks will decrease, which in turn will improve overall network reliability and reduce power consumption as well as operational expenditure. After reviewing the state-of-the-art in SDMfiber research and development with a particular focus on weakly coupled single-mode multi-core fibers, we take a look beyond the capabilities of SDM as a means of boosting transmission capacity and discuss ideas and concepts on howto exploit the spatial dimension for improved efficiency and resource sharing in optical networks.

Comparing inter-core skew fluctuations in multi-core and single-core fibers

We measure the dynamic skew fluctuations between cores in a multicore fiber and show that they are more than one order of magnitude smaller than those of parallel single-core fibers over a 24 hour period.

Spectrally efficient enhanced-performance bidirectional coherent PON with laserless 10 Gb/s ONU [invited]

We present and experimentally characterize a spectrally efficient, bidirectional, ultradense wavelength-division multiplexing passive optical network (PON) (2 × 120 Gb/s at 50 GHz) over 30 km standard single-mode fiber. This is achieved using a 4 GHz grid with partial spectrum overlapping, Nyquist-shaped 16-ary quadrature amplitude modulation, and digital frequency shifting. This scheme is based on a laserless, self-homodyne PON with centralized wavelength control. We achieve reduced impact of the Rayleigh back-scattering effect due to Nyquist-pulse shaping and frequency upshifting. Self-homodyne detection relaxes the laser linewidth requirement and digital signal processing complexity at the optical network unit. To demonstrate the extra benefit of the proposed PON system, we also experimentally and theoretically evaluate the impact of nonlinear Raman crosstalk in video overlay. Compared to a baseband Nyquist signal and baud rate non-return-to-zero equivalent, the proposed system improves the carrier-to-Raman crosstalk ratio of video overlay by 4 and 6 dB, respectively.

Single parity check multi-core modulation for power efficient spatial super-channels

We investigate multi-core modulation formats for spatial super-channels using a single parity check on PDM-QPSK symbols. Compared to per-core PDM-QPSK, we show improvements in required OSNR of up to 1.8 dB, with minimal impact on spectral efficiency.

Self-homodyne coherent OFDM packet transmission without carrier frequency or common phase error estimation

We report self-homodyne transmission of coherent OFDM packets with polarization multiplexed pilot tone, using a 530kHz linewidth laser. Error free operation is achieved without carrier frequency or common phase error estimation.

Impact of inter-core crosstalk on the transmission distance of QAM formats in multi-core fibers

We investigate the transmission distance of three QAM modulation formats, in the presence of inter-core crosstalk in a 7-core fiber. We show that crosstalk limits transmission distance for all formats with a greater impact on higher order modulation formats. For a crosstalk level equivalent to equal signal launch power in each core, we measure a reduced transmission distance at BER=1.5×10-2 of 17%, 23% and 36% for PDM-QPSK, PDM-16QAM and PDM-64QAM respectively.

Coherent Detection in Self-Homodyne Systems With Single and Multi-Core Transmission

This work reviews the latest advancements in coherent self-homodyne detection (SHD) using signals with polarizationor space-multiplexed pilot tones (PTs) originating from the same light source, towards the implementation of low-cost coherent receivers. The coherency between signals and PTs drastically reduces laser linewidth requirements, enabling the use of high-order modulation formats with low-cost DFB lasers. In this work, we revise the application of SHD in high-capacity space-division multiplexed links using multi-core fibers, outlining optical signal-to-noise ratio, skew and phase noise requirements of such systems. Furthermore, we evaluate the application of SHD for the implementation of laser-less optical network units in passive optical networks, as well as recent developments in digital SHD techniques.

Homogeneous, single-mode MCF transmission

We discuss the possibility of multi Pb/s transmission using homogeneous, single-mode, multi-core fibers. We outline the key components of a recent demonstration, the consequences of fiber properties such as inter-core crosstalk and skew and potential for even greater efficiency from spatial-superchannel transmission.