Using a fully automated rotational alignment algorithm and a portable 3-electrode arc-discharging fusion splicer, we achieve median splice losses of 0.13 dB between antiresonant hollow-core fibers within 120 seconds with 100% success rate.

Using a novel azimuthal alignment algorithm and side-view images, we reliably determine the polarity and twist rate of multicore fiber and achieve average losses as low as 0.03 dB using a 3-electrode arc-discharging fusion splicer.

Multicore fiber is a promising spatial division multiplexing technology to increase the transmission bandwidth of optical fiber links in any given available spatial cross section. To connect multicore fibers, similar to single-core fibers, fusion splicing is an indispensable tool. Since multicore fibers cannot be circularly symmetric, precise transverse and azimuthal alignment is crucial to minimize the insertion loss penalty that would originate from even small offsets in the core locations of the two fibers to be spliced together. In this paper, a novel azimuthal alignment algorithm for multicore fiber splicing is presented. Since it is based on side-view images, it can also determine the twist rates of both fibers to be spliced and take these twist rates into account when calculating the optimum azimuthal alignment angle at the very ends of the two fibers. In the case of fibers with markers, i.e., fibers that are not rotationally symmetric, the relative and absolute polarities of the two fiber ends are computed as well. We present the formulation of the azimuthal alignment algorithm and demonstrate its stability and versatility for a wide range of fibers with vastly different geometries, core numbers and twist rates, including an offset single-core fiber. In the case of 4-core fibers with markers, we achieve average splice losses of less than 0.03 dB regardless of the polarity, which is a substantial advantage in terms of real-world applicability in the field. For a twisted 7-core fiber, we demonstrate an accurate twist rate detection with standard deviation < 1.4/m (turns per meter).

We present a novel azimuthal alignment algorithm for multicore fiber splicing that separates the core and marker information in side-view images. For two different 4-core fiber designs, average fusion splice losses of less than 0.03 dB are demonstrated using a 3-electrode arc-discharging fusion splicer.

It has become increasingly difficult to increase the capacity of a submarine cable by simply increasing the spectral efficiency (SE) over a single fiber pair, due to its logarithmic dependence on the signal-to-noise ratio (SNR). A widely recognized alternative is to use spacedivision multiplexing (SDM) which increases the number of fiber pairs, resulting in a linear increase in SE. Increasing capacity by adding fiber pairs while cost-reducing the repeater and cable presents a complex optimization problem. In this paper, a techno-economic model based on the Gaussian Noise (GN) model is used to study the optimum fiber pair count and the impact of fiber properties on the cost-per-bit (CPB). Studies include cost and performance tradeoffs from pump-sharing in the amplifiers, limitations on optical launch power from power feed and 980nm pump size, and the resistance per unit length of the cable. Advanced fibers with ultra-low loss, ~0.155 dB/km, exhibit 8-10% capacity and CPB advantage over fibers with ~0.170 dB/km loss in all cases. Furthermore, in spite of launch power limitations, it remains beneficial for capacity and CPB to maintain a larger effective area, i.e. to use G.654.B/D fibers, for up to ~24 fiber pairs.

This paper describes the enabling fiber and amplifier technologies for ultra-long reach unrepeatered transmission submarine cable systems. The key enabling technologies include the large-area ultra-low attenuation fibers, high-efficient Remote Optically Pumped Amplifier (ROPA), and second order pumped distributed Raman amplification. The benefits of the technologies are illustrated, and their physical limiting factors for unrepeatered transmission are discussed. We then present the design and experimental demonstrations of ultra-long reach total capacity of 400 Gb/s (4 x 100 Gb/s) unrepeatered transmission links with real-time signal processing. The unrepeatered transmissions are achieved by using commercially available large-area ultra-low attenuation fibers and transceiver modules. This 4 x 100 Gb/s unrepeatered transmission over 557 km fiber is demonstrated with single fiber configuration. TeraWave SCUBA150 fibers with an effective area of 153 mu m(2) and an average attenuation of 0.153 dB/km at 1550 nm, and forward and backward ROPAs with second-order Raman pumping schemes are employed in this demonstration. Long-term real-time error free transmission results are also reported. In addition, we report the experimental demonstration of real-time transmission of 4 x 100 Gb/s unrepeatered link over 578 km fiber by employing an additional dedicated pump fiber path.

We demonstrate 2400 km mode-multiplexed 16-QAM transmission over a low DMGD (27.1 ps/km) and low MDL (1.75 dB) 3-mode fiber link. The large effective-area 3-mode fiber is shown to outperform a standard single-mode fiber for distances up to 4500km.

It is possible to create advanced, manufacturable designs for both single- and multi-mode optical fibers that give significant performance improvements in transmission. This tutorial gives practical illustrations for both datacom and coherent long haul applications.

The 53.125 Gbps transmission is experimentally investigated over a next-generation wideband multimode optical fiber (NG-WBMMF) using transmitter optical sub-assemblies (TOSAs) and wideband receiver optical sub-assemblies (ROSAs) developed for 25 Gbps short wavelength division multiplexing (SWDM) operation. A commercial 100 Gbps four-level pulse amplitude modulation integrated circuit (PAM4 IC) evaluation kit with real-time digital signal processing (DSP) is used. Dual wavelength transmission (2 lambda x 53.125 Gbps) tests over 300 m of NG-WBMMF are carried out for the wavelength pairs 850, 880 nm and 910, 940 nm with a 4 x 1 optical MUX/DeMUX in the link. Measured pre-forward error correction (FEC) bit error ratio (BER) below the KP4 FEC threshold of 2.4 x 10(-4) indicates the feasibility of 100/200 Gbps transmission over NG-WBMMF using a PAM4 chipset with real-time DSP. Single wavelength transmission (1 lambda x 53.125 Gbps) using long wavelength TOSAs at 976 and 1066 nm is also studied. Pre-FEC BER below 2.4 x 10(-4) is achieved over 300m at 976 nm and 200 m at 1066 nm. Single wavelength tests from 850 to 940 nm had the same results as the 976 nm wavelength. Thus, this is the first experiment which shows the potential of 400 Gbps transmission with eight SWDM wavelength windows over a single NG-WBMMF using SWDM TOSAs, ROSAs, and commercial 100 Gbps PAM4 chipset.

Two system transmission experiments are reported which indicate the feasibility of transmitting an aggregated speed of > 200 Gb/s over a single next-generation wide-band multimode optical fiber (NG-WBMMF) using a shortwave wavelength division multiplexing (SWDM) and a four-level pulse amplitude modulation (PAM4), using optics rated for 25 Gb/s NRZ operation. The first experiment leverages predistorted KR4 51.5625 Gb/s electrical PAM4 signaling generated by an arbitrary waveform generator to drive SWDM TOSAs at 850, 880, 910, and 940 nm. The received optical PAM4 signals are then post processed offline with linear equalizers to improve the eye quality. Detailed analysis of the height and width of the received optical eyes indicates an aggregated 206.25 Gb/s speed is achievable on a single NG-WBMMF beyond 150 m. In the second experiment, a commercial PAM4 IC evaluation kit with real-time digital signal processing is adopted to generate and detect PAM4 signals at KP4 FEC rate of 53.125 Gb/s per wavelength. The SWDM wavelength range is extended with additional tests at 980 nm. Pre-FEC BER below threshold of 2.4 x 10(-4) is achieved up to 300 m across all five wavelengths demonstrating an aggregated speed of 265.625 Gb/s over a single MMF.

This paper reviews recent progress on ultralarge-area low-loss fibers for next-generation high-capacity terrestrial long-haul optical networks. The key optical fiber properties of new class fibers are described, and their impact on the transmission performance for 400 Gb/s polarization-multiplexed multilevel modulation coherent transmissions is discussed. The practical consideration of the large-area fibers, such as splicing and cabling for terrestrial transport systems, is also briefly addressed. In addition, we describe two advanced optical fiber amplifier technologies that will improve the efficiency in utilization of optical networking and reduce total system costs. The design and performance of an arrayed optical fiber amplifier using a compact ribbonized Er-doped fiber (EDF) for next-generation reconfigurable optical add/drop multiplexer nodes are discussed, and the performance characteristics of complementary Raman/EDFA, which has +70 nm bandwidth for seamless C+L-band transmissions, are described. Finally, we present the experimental demonstration of transmission of 34.6 Tb/s in 70 nm single band over 2400 km fiber.

Today coherent transport technology enables 40 and 100 Gigabit per second speeds over legacy fiber networks, but soon new developments will enable even higher data rates up to 400 Gb/s and beyond over a new generation of low loss, large area fibers. In response to the advances in signaling technologies, OFS introduced the TeraWave ULL Optical Fibers designed for emerging terabit per second modulation formats. The deployment of cable including TeraWave ULL Optical Fiber will help network operators better manage emerging, fundamental limitations in spectral efficiency and un-regenerated reach to help reduce cost-per-bit of transport as traffic grows exponentially. TeraWave ULL Optical Fiber transports coherent modulation formats almost twice as far as the installed base of G.652 standard single-mode fiber (SSMF) without regeneration. It has been optimized for use in both the Cand L-bands. The costper-bit from procuring and fully lighting a cabled TeraWave ULL Optical Fiber can be 40 to 80% lower cost-per-bit than fully lighting a legacy G.652 fiber over an erbium-doped fiber amplifier (EDFA) chain, typical of the installed base, by avoiding the high cost of regeneration.

We will discuss design principles and properties of large effective area, low loss fibers for C+L band transmission. These fibers need to have excellent cabling properties from 1530 to 1610nm.

We measured the guided acoustic-wave Brillouin scattering in a few-mode fiber that supports LP01 and LP11 modes. We observed a strong correlation between the acoustic modes and optical intramodal and intermodal Brillouin scattering.

This chapter gives an overview of design and optimization of few-mode optical fibers (FMF) for space-division multiplexed transmission. The design criteria are outlined, along with performance limitations of the traditional step-profile and graded-index profiles. The trade-offs between number of usable optical modes (related to total channel capacity), differential group delay, differential mode attenuation, mode coupling, and the impact on MIMO (multiple-input and multiple-output) receiver complexity are outlined. Improved fiber designs are analyzed which maximize channel capacity with foreseeable next-generation receiver technology. FMF measurement technology is overviewed.

The design of few-mode fibers will be discussed from the point of view of key attributes and fundamental limitations. We will consider the maximum number of modes that might be supported in a practical fiber.

We experimentally demonstrate multiple-input multiple-output transmission over a 209-km hybrid few-mode fiber span of a combined 3-space-, 2-polarization-, and 5-wavelength-division multiplex, using low-loss 3-spot mode couplers and backward-pumped distributed Raman amplification.