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Nonlinear interaction between signal channels may result in significant performance degradation in transoceanic dense wavelength-division-multiplexing (WDM) transmission systems operated at high bit rates. In this paper, we report that the nonlinear crosstalk for systems with high spectral efficiency can be suppressed if WDM channels are launched with orthogonal relative states of polarization. It is shown that for adjacent channels (that experience the strongest nonlinear interaction) the launched relative state of polarization is maintained over the large distance of low polarization-mode dispersion fiber typically used in undersea systems. Numerical studies, as well as experimental results, are presented for standard and dispersion slope-matched dispersion maps.

We present ultra-long-haul transmission experiments using an enhanced conventional fiber with - 14-ps/nm/km dispersion coefficient. This new fiber allows for novel dispersion maps with improved transmission performance compared to dispersion maps based on nonslope matched submarine fiber, and similar performance to dispersion flattened maps.

Using single-stage C-band EDFAs equalized to 41 nm, we transmit 152 x 200 Gb/s PDM 16QAM channels with 6.0 b/s/Hz spectral efficiency over 9,748 km enabled by Nyquist spectral shaping and digital back propagation. 76 x 400 Gb/s channels are also transmitted over 8,665 km detecting two 200 Gb/s channels simultaneously using a single wideband receiver. Digital back propagation benefit versus channel pre-emphasis, transmission distance and wavelength are experimentally investigated.

The rapid growth of long-haul wavelength-division multiplexing (WDM) fiber-optic telecommunications challenges lightwave system designers to increase the transmission capacity per fiber pair, while reducing the time to market. This makes it essential to have fast and accurate computer modeling tools to aid the systems design. There is a natural engineering tradeoff between simulation speed and accuracy; fast approximations tend to be inaccurate, while the exact treatment of the physical processes affecting transmission are nearly impossible to capture in a time-efficient algorithm. The proof of a successful tool development lies in the comparison of simulation results to transmission system measurements. In this paper, we discuss a new simulation technique based on careful evaluation of the key physical effects that produce system impairments. We show that this new approach can produce fast and accurate simulations of long-haul WDM transmission systems.

We introduce a signal processing approach to compensate for the timing jitter produced by the acoustic effect in soliton communications. The other main sources of timing jitter, the Gordon-Haus effect and the polarization effect, are inherently stochastic. By contrast, the acoustic effect is deterministic and becomes the dominant source of bit error rates in standard soliton systems when the bit rates are more than 10 Gb/s and the transmission distance is more than several thousand kilometers. We exploit the deterministic nature of the acoustic effect to introduce a scheme that predicts the amount of timing jitter as a function of the previous transmitted bits and uses the information to adjust the sampling period of the received soliton pulses. We demonstrate successful application of the scheme by simulations and discuss implementation issues.

We numerically analyze the effectiveness of a nonlinear optical loop mirror (NOLM) based on standard communication fiber with randomly varying birefringence for demultiplexing streams of picosecond pulses at 100 GHz. A broad switching window of about three pulse full-width at half maximum (FWHM) can be obtained. The device performance is defined by the pulse duration, the dispersion of the fiber, and the fiber length. We show that imperfect averaging of the randomly varying birefringence causes amplitude fluctuations on the NOLM transmission curve. We also show that the Raman self-frequency shift does not affect the NOLM switching characteristics at picosecond pulse durations.

We experimentally investigate digital back propagation (DBP) benefit versus channel preemphasis, average launch power per channel, and transmission distance. We find the DBP benefit scales monotonically with channel power and transmission distance. Measurement results match well with theory.

Lignin is one of the most abundant biopolymers. It accounts for up to 25% of plant biomass in the biosphere. Lignified cell walls represent an important evolutionary step in plant adaptation to land life. This adaptation provided structural support, nutrient transport, protection from UV radiation, desiccation stress and protection from herbivores and pathogens. Due to lignin’s long half-life, it has become a major carbon sink, causing depletion of the CO2 levels and an increase in O2 levels. Currently lignin research is important for the forage and biofuel industries. It has been seen that a reduction in lignin content leads to higher digestibility and higher release of cellulose from plants. Caffeoyl coenzyme A O-methyltransferases (CCoAOMTS) are a class of enzymes that transfer a methyl group from S-adenosylmethionine to an alcohol group. These enzymes are necessary for lignin production in plants. Previous work has shown that knocking down the function of this enzyme in higher plants caused a decrease in lignin content. Physcomitrella patens is a moss, which is considered not to synthesize lignin but it contains genes for the full lignin biosynthesis pathway. Currently there is some evidence of lignin-like compounds occurring in moss, but evidence of a truly lignified cell wall does not exist. This study looks at two specific enzymes from Physcomitrella patens, Pp-OMT1 and Pp-OMT2. These enzymes resemble CCoAOMTs. Both enzymes were tested for substrate specificity and compared to a true caffeoyl coenzyme A O-methyltransferase from Arabidopsis thalina, AtCCoAOMT1. Furthermore kinetics of Pp-OMT2 and AtCCoAOMT1 were compared. Our results showed that Pp-OMT2 is likely to be a true CCoAOMT while Pp-OMT1 is not.

We transmit 441 × 100 Gb/s signals in 9 THz of optical bandwidth over 9,100 km at a SE of 493% and a bitrate-distance product >400 Pb/s*km. Our 60% overhead coded modulation format achieves a 3.35 dBQ error correction threshold at an OSNR that is within 2.5 dB of the Shannon limit for the targeted SE. All channels are decoded with no errors.

The development and deployment of coherent transponders will lead to an order of magnitude increase in the capacity of transoceanic systems. To satisfy future capacity demands new technologies will be needed.

We transmit 160 x 100 G PDM RZ 16 QAM channels with 5.2 bits/s/Hz spectral efficiency over 6,860 km. There are more than 3 billion 16 QAM symbols, i.e., 12 billion bits, processed in total. Using coded modulation and iterative decoding between a MAP decoder and an LDPC based FEC all channels are decoded with no remaining errors.

A dispersion map that meets the conflicting needs of coherent and direct detection transmission is presented. Performance improvements over a conventional map are verified for coherent transmission by experiments and simulations.

Using DSP and DACs we create 100G PDM 16QAM signals with nearly rectangular spectra at 16.64 GBd symbol rate on 17 GHz spacing achieving a spectral efficiency of 6.1 bits/s/Hz. We transmit 294 of these channels over 6,630 km in 5 THz (40 nm) bandwidth using single stage C-band EDFAs. All channels are decoded with no errors.

One of the main mechanisms that limits the bit rate and transmission distance in soliton communication lines is the so called “long-range” interaction of solitons [1]. The physical reason of this interaction is the electrostrictional excitation of the acoustic waves by light pulses and back-influence of the acoustic wave on solitons [2]. In soliton communication lines the interaction of solitons with the acoustic wave results in the additional to the Gordon-Haus effect [3] timing jitter of solitons [4,5]. Although the timing jitter of solitons can be significantly reduced by guiding filters [6], the detailed investigation of the acoustic effect is still important because the guiding filters cannot totally suppress the timing jitter.

We demonstrate a pilot-symbol assisted joint polarization carrier phase estimation technique that detects cycle slip and avoid error propagation. Coherent detection without differential coding is feasible when the cycle slip probability is less than 10−3.

We transmit 198x100G pre-filtered PDM-RZ-QPSK channels with 400% spectral efficiency over 6,860 km. We also show that 100G coherent nonlinear performance scales differently with distance on uncompensated dispersion maps than expected from direct-detection transmission.

We investigate the spectral efficiency (SE) limit of pre-filtered modulation in optical fiber communication systems. We show that pre-filtering induced symbol correlation generates a modulation with memory and, thus, a higher SE limit than that of the original memoryless modulation. The SE limits of a series of modulation formats with varying number L of correlated symbols producing 50% of the original bandwidth are evaluated, which approach the SE limit of a modulation format with 50% pre-filtering as L → ∞. We show that the SE limit of a modulation format with L correlated symbols approximates a lower bound for the SE limit of the corresponding pre-filtered format.

We propose a high spectral efficiency transmission scheme employing tight pre-filtering and maximum-a-posteriori-probability (MAP) detection. We demonstrate that pre-filtering induced inter-symbol-interference can be effectively compensated with MAP detection after transoceanic transmission.

We transmit 112×112 Gb/s pre-filtered PDM RZ-QPSK channels with 360% spectral efficiency over 9,360km with the channel spacing set to the baud rate. This results in a record spectral efficiency for transpacific distance.

The deployment of 10 Gb/s RZ-DBPSK transponders has led to high capacity transoceanic systems To satisfy future capacity demand, high spectral efficiency systems that operate at 40 G and 100 G rates using polarization multiplexing will be required.

We study transmission of 40 Gb/s signals using coherent RZ-QPSK with and without polarization multiplexing using 100km large effective area fiber-spans and dual-stage EDFAs with mid-stage dispersion compensation. We show advantage and disadvantage of coherent detection schemes.

• The fiber's nonlinear index is ALWAYS bad⋆ ! Thus, all transmission formats (including solitons) attempt to manage the fiber's nonlinear index. • The fiber's nonlinear index must be considered together with the fiber's dispersion.

The capacity demands for future undersea cable networks will push the industry to WDM spectral efficiencies in excess of 1-B/s/Hz. This will require significant progress in optical fibers and signal processing.

Summary form only given. Solitons that propagate in an optical fiber experience timing jitter that limits both the bit rate and the information transmission distance. This timing jitter is caused by several effects: the Gordon-Haus effect, the polarization effect, and the acoustic effect. At bit rates in excess of 10 Gbit/s, the acoustic effect becomes the dominant cause of the timing jitter at distances greater than a few thousand kilometers. The acoustic effect is created by the large transverse gradient of the electric fields in the optical fiber due to the soliton pulses. These large field gradients electrostrictively excite acoustic waves that influence later solitons. The acoustic wave perturbs the effective refractive index of the fiber, leading to changes in the frequencies and temporal locations of the solitons.

We present a theory of acoustically induced pulse interaction in a ring fiber laser cavity. In most cases the acoustic interaction leads to pulse bunching, but in some cases it leads to regular pulse spacing. Our results compare well with the experimental data.