We review the latest advances on ultra-high throughput transmission using crosstalk-limited single-mode multicore fibers and compare these with the theoretical spectral efficiency of such systems. We relate the crosstalkimposed spectral efficiency limits with fiber parameters, such as core diameter, core pitch, and trench design. Furthermore, we investigate the potential of techniques such as direction interleaving and high-order MIMO to improve the throughput or reach of these systems when using various modulation formats.
We describe a number of experiments demonstrating and exploring the potential of combing wideband-optical comb sources with space-division multiplexed transmission systems and in particular with homogeneous-single-mode multicore fibers including Pb/s transmission using conventional receiver technology without MIMO processing and longdistance recirculating transmission. We describe experiments using synchronized parallel transmission loops to investigate joint processing of spatial super channels and multi-dimensional modulation before discussing how optical comb technology may combine with SDM fibers to allow comb re-generation across networks to enable high-order modulation with simplified DSP. Overall, these experiments demonstrate a range of scenarios where the combination of optical combs and homogeneous MCFs can be advantageous in future optical communications networks.
High-capacity fiber-optic communications are promising technologies to satisfy people’s continuously growing demands for bandwidth hungry data services. Multi-wavelength optical circuit switching (OCS) technology is already widely deployed, however, with the limited number of transceivers equipped at each optical node and other constraints, the number of lightpaths which can be established and employed simultaneously in an optical network is restricted. This reduces the utilization efficiency of wavelength resources. Comparing to OCS, dynamic optical switching systems such as optical packet switching (OPS) offer higher efficiency in terms of wavelength resource utilization and have the potential to share more of the wavelength resources on fiber-links between larger numbers of users simultaneously. In such networks, bursty input signals or changes in traffic density may cause optical power surges that can damage optical components or impose gain transients on the signals that impair signal quality. A common approach for reducing gain transients is to employ electrical automatic gain control (AGC) or optical gain-clamping by optical feedback (OFB). AGC may be limited by the speed of the feedback circuit and result in additional transients. Meanwhile OFB can clamp the gain of power varying optical signals without transient but can introduce amplitude fluctuations caused by relaxation oscillations in the lasing cavity for large input power fluctuations. We propose and demonstrate a novel scheme for suppressing the power transients and the relaxation oscillations. This scheme can be utilized in optical amplifiers even if the optical feedback is employed.
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.
In this work the performance of annealed proton-exchanged (APE) waveguides in periodically poled stoichiometric lithium tantalate (PPSLT) for high power applications in the C-band is investigated. Two APE-PPSLT chips comprising 50 waveguides produced with different poling periods and mask width for proton-exchange (PE) were characterized. The performance of the PPSLT devices was also compared with a periodically poled lithium niobate (PPLN) waveguide. Despite lower efficiency, no photorefractive issues or deleterious green light emission were observed in the PPSLT waveguides. The experimental results suggest that the homogeneity of the PPSLT waveguides can be further improved, which will enhance their efficiency.
Current optical transport networks provide high bandwidth through the use of advanced WDM technology, but are difficult to adapt to the different statistical patterns and quality of service (QoS) demands of future traffic. There has been much debate whether the use of dynamically reconfigurable optical networks would have a number of advantages in accommodating the needs of future traffic demands. Dynamic networks would eliminate the need for frequent opto-electronic conversion in current networks, and may save resources through higher utilization and fast adaptation. Different architectures have been proposed to address this problem: Wavelength-routed optical networks (WRON), optical burst switching (OBS), and optical packet-switching (with increasing granularity and speed of reconfiguration). In this paper we investigate whether these architectures are suitable (necessary?) to meet the demands of future traffic, using an analysis focusing on both modeling and experimental aspects.