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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 × 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 × 100 Gb/s unrepeatered transmission over 557 km fiber is demonstrated with single fiber configuration. TeraWave SCUBA150 fibers with an effective area of 153 μm2 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 × 100 Gb/s unrepeatered link over 578 km fiber by employing an additional dedicated pump fiber path.

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.

We demonstrate unrepeatered transmission of 400Gb/s $(4\times 128Gb/s)$ over 557km and 100Gb/s over 590km distance with single fibre configuration using forward and backward ROPAs enabled by 2nd-order Raman pumping and large $A_{eff}$ ultra-low-loss fibre.

We demonstrate real-time transmission of 16 Tb/s (80x200Gb/s) over 1020km TeraWave ULL fiber with 170km span length using the world's first 200Gb/s CFP2-DCO module with a record low power consumption less than 0.1W/Gbps.

We demonstrate transmission of 78×256Gb/s PM-16QAM over 4800km, and 78×192Gb/s PDM-8QAM over 7200km with 100km span length at spectral-efficiency 6.0 and 4.5 b/Hz/s, respectively. This is achieved by ultra-large-A eff ultra-low-loss fibre using EDFA-only for amplification.

We demonstrated 6.3-Tb/s (63 × 128 Gb/s) unrepeatered transmission over 402-km fiber link. This was achieved by employing a high-power Yb-free clad-pumped L-band erbium-doped fiber amplifier (EDFA) as a booster amplifier in the transmitter station, a combination of ultralarge-area fiber, low loss and zero-water-peak loss fibers, and a remote optically pumped amplifier (ROPA), which was counter-propagating second-order Raman pumped from receiver station. This letter also describes the design and characteristics of Yb-free cladpumped L-band EDFA, and discusses the system performance optimization of ROPA and Raman impact on large capacity long reach unrepeatered transmission.

We demonstrated 3.2-Tb/s (32 × 120-Gb/s) unre-peatered transmission over 445-km fiber with Aeff-managed-span. This was achieved by employing co-propagating second-order pumped Raman amplification and remote optically pumped amplifier, which was counter-propagating second-order Raman pumped. This letter also discusses design tradeoff on the nonlinear tolerance and Raman gain efficiency within Aeff-managed-span for performance enhancement of unrepeatered transmission.

We demonstrate unrepeatered transmission of 8x128Gb/s PDM-QPSK signals over a 515k-m fiber link. This ultra-long distance of 800 Gb/s unrepeatered transmission in a single fiber configuration is achieved by employing enabling techniques such as large-effective-area ultra-low-attenuation fibers, co-propagating and counter-propagating 2nd-order-pumped distributed Raman amplification, and remote optically pumped amplifier (ROPA). The ROPA itself is also counter-propagating 2nd-order Raman pumped. The designs and characteristics of the ROPA and 2nd-order pumped distributed Raman amplification are described, and optimization of the transmission performance of this ultra-long reach 800Gb/s unrepeatered transmission fiber link is discussed in this paper.

We present results on broadband transmission through photonic crystal waveguide bends optimized for slow-light modes. Theoretical analysis and topology optimization are complemented by experimental verification of designs fabricated in SOI material.

We report the design, fabrication and characterization of a photonic crystal directional coupler with a size of ∼20×20 μm2fabricated in silicon-on-insulator material. Using a scanning near-field optical microscope we demonstrate a high coupling efficiency for TM polarized light at telecom wavelengths. By comparing the near-field optical images recorded in and after the directional coupler area, the features of light distribution are analyzed. Finally, the scanning near-field optical microscope observations are found to be in agreement with the transmission measurements conducted with the same sample.

Unrepeatered transmission of 6.3-Tb/s (63x128-Gb/s) signals over 402-km of effective-area (Aeff) managed fiber link is achieved by employing high power Yb-free clad-pumped L-band EDFA and remote optically pumped amplifier, which is counter-propagating 2nd-order Raman pumped.

We demonstrate a novel polarization splitter based on a two-dimensional grating etched in a silicon-on-insulator waveguide. The device couples orthogonal modes from a single-mode optical fiber into identical modes of two planar ridge waveguides. The extinction ratio is better than 18 dB in the wavelength range of 1530-1560 nm and the coupling efficiency is approximately 20%. The device is very compact and couples light only to transverse-electric modes of the planar waveguides. Therefore, it may be used in a polarization diversity configuration to implement a polarization insensitive photonic integrated circuit based on photonic crystal waveguides.

We report 8×100km transmission of five 450Gbits/s PDM-32QAM DWDM signals over ultra-large-area fiber and one 50GHz-grid WSS-based ROADM at 8.4b/s/Hz spectral efficiency, enabled by the combined use of electrical and optical spectral shaping techniques.

We report on time-of-flight experimental measurements and numerical calculations of the group-index dispersion in a photonic crystal waveguide realized in silicon-on-insulator material. Experimentally group indices higher than 230 has been observed. Numerical 2D and 3D time-domain simulations show excellent agreement with the measured data.

Several planar photonic crystal components topology-optimized for TE-polarized light, including 60 masculine bends, Y-splitters, and 90 masculine bends, have been characterized for the TM polarization. The experimental results are confirmed by finite-difference time-domain calculations. The surprising efficiency for TM-polarized light is found and paves the way for photonic crystal components suitable for both polarizations.

Topology optimization is used to design a planar photonic crystal waveguide component resulting in significantly enhanced functionality. Exceptional transmission through a photonic crystal waveguide Z-bend is obtained using this inverse design strategy. The design has been realized in a silicon-on-insulator based photonic crystal waveguide. A large low loss bandwidth of more than 200 nm for the bandgap polarization is experimentally confirmed.

Planar photonic crystal waveguide structures have been modelled using the finite-difference-time-domain method and perfectly matched layers have been employed as boundary conditions. Comprehensive numerical calculations have been performed and compared to experimentally obtained transmission spectra for various photonic crystal waveguides. It is found that within the experimental fabrication tolerances the calculations correctly predict the measured transmission levels and other major transmission features.

We have investigated the properties of TM polarized light in planar photonic crystal waveguide structures, which exhibit photonic band gaps for TE polarized light. Straight and bent photonic crystal waveguides and couplers have been fabricated in silicon-on-insulator material and modelled using a 3D finite-difference-time-domain method. The simulated spectra are in excellent agreement with the experimental results, which show a propagation loss as low as 2.5+/-4 dB/mm around 1525 nm and bend losses at 2.9+/-0.2 dB for TM polarized light. We demonstrate a high coupling for TM polarized light in a simple photonic crystal coupler with a size of ~ 20 m x 20 m. These promising features may open for the realization of ultra-compact photonic crystal components, which are easily integrated in optical communication networks.

As deployment of fiber to the home (FTTH) within multiple dwelling units (MDUs) is growing, more technicians will be involved in the deployment of optical drop cables, and there is a desire to use craft and practice similar to what is used for copper cables. We introduce a solid bend insensitive fiber in this application that is backwards compatible to G.652D fiber, and has macrobending, splice loss and system performance to meet the very demanding conditions of these applications. A closer look at the demands of this environment has made it necessary to re-evaluate reliability in these critical applications. We apply the Power Law Model to predict reliability in these demanding applications, and provide experimental evaluation of the model through testing on optical fibers and cables. It will be shown that bends and tension need to be considered together when evaluating the reliability of the passive optical plant.

Solid fibers with greatly reduced bend loss are presented. Ring-assisted fibers provide enhanced cutoff, allowing .01dB / turn cable losses around a 9.5 mm mandrel while meeting cutoff and MFD standards and avoiding potential problems with holes.

Ring-assisted fibers suppress unwanted modes, improving the tradeoff that limits bend loss. Fabricated fibers achieve low bend loss and compatibility with standard fibers required for fiber to the home.

We present a far-field optical technique allowing measurements of the dispersion relation of electromagnetic fields propagating under the light cone in photonic nanostructures. It relies on the use of a one-dimensional grating to probe the evanescent tail of the guided field in combination with a high-numerical-aperture Fourier- space imaging setup. A high-resolution spectroscopy of the far-field emission diagram allows us to accurately and efficiently determine the dispersion curve and the group-index dispersion of planar photonic crystal waveguides operating in the slow-light regime.

The propagation of light in photonic structures is governed by the dispersion curve omega(k) relating the frequency omega to the spatial wave vector k. Engineering the slope of the dispersion curve allows to implement innovative concepts such as slow light in coupled resonators, with surface plasmons or in photonic crystal structures. In this context, some important regions of the dispersion curves lie outside of the light cone, implying that the associated modes do not radiate into free space and as a result propagate with minimal optical losses. In this work, we demonstrate that far-field optical experiments can be used to accurately extract the dispersion curve of a slow mode propagating below the light cone in a planar nanophotonic waveguide. The combination of an end-fire set-up working in the 1.5 mum range, generally used to measure the transmission through the waveguide, along with a high numerical aperture Fourier space imaging set-up and an integrated linear probe grating (LPG), allows a fine spectral analysis of each mode of the photonic structure. As an example, we measured the dispersion curve of a specially designed single defect photonic crystal (PhC) waveguide (SW1). The PhC waveguide has been engineered to operate in a slow-light regime over a large frequency bandwidth, by changing the diameter of the first and second row of holes in a conventional W1 PhC waveguide.

A photonic-crystal waveguide sensor is presented for biosensing. The sensor is applied for refractive index measurements and detection of protein-concentrations. Concentrations around 10 μg/ml (0.15μMolar) are measured with excellent signal to noise ratio, and a broad, dynamic refractive index sensing range extending from air to high viscous fluids is presented.

The paper presents specific protein detection with a planar photonic crystal waveguide (PC-WG) sensor. The advantages of the device we suggest are that it is realized in silicon and can be integrated on a SOI-wafer (silicon-on-insulator) along with other electronic and optical devices. Thus, the fabrication technology used for the sensor is the same as for CMOS electronic devices. The PC-WG can be made very compact and the sample volume to be analyzed can also be reduced considerably compared to many other biosensors presented in the literature.

Topology optimization has been used to design intersections and bends in two-dimensional photonic crystal slab waveguides. We have experimentally confirmed that the optimized intersection displays high transmittance with low crosstalk for the straightforward beam line.

We report thorough investigations of photonic crystal waveguide properties in the slow light regime. The transmission and the group index near the cutoff wavelengths oscillate in phase in close analogy with the 1D photonic crystal behavior. The influence of having a finite number of periods in the photonic crystal waveguide is addressed to explain the spiky character of both the transmission and group index spectra. The profile of the slow-light modes is stretched out into the first and second rows of the holes closest to the waveguide channel. One of our strategies to ameliorate the design of photonic crystal devices is to engineer the radii of holes in these rows. A topology optimization approach is also utilized to make further improvements. The results of the numerical simulations and the optical characterization of fabricated devices such as straight waveguides with bends and couplers are presented. A nice match is found between theory and experiment.

Numerical and experimental studies on the photonic crystal waveguide intersection based on the topology optimization design method are reported and the effectiveness is shown by achieving high transmission spectra with low crosstalk for the straightforward beam-propagation line.

A two-dimensional photonic crystal (2DPC) slab waveguide-based symmetric Mach-Zehnder type all-optical switch (PC-SMZ) is promising for a future ultra-fast photonic network system. An ultra-fast (~ ps) and ultra-low energy (~ 100 fJ) switching has already been demonstrated as the 1st phase. The 2nd phase is to create a PC SMZ-based ultra-fast photonic logical switch with a latch function for an ultra-fast photonic digital processor. One of the steps towards the goal is to develop a new design method of waveguides with wide/flat bandwidth, high transmittance and low reflectivity for improving switching performances. Another one is to develop a selective area growth of quantum dots. This paper dominantly reviews these two recent topics as well as briefing the PC-SMZ performances.

In this paper, we have employed a collection scanning near-field optical microscope (SNOM) for imaging of the propagation of light at telecommunication wavelengths along straight and bent photonic crystal (PC) waveguides with Y-splitters, Z-bends and simple couplers that were fabricated on silicon-on-insulator (SOl) wafers

In this work, we have experimentally and by simulations investigated the effect of making small perturbations of the size of the border holes adjacent to the planar photonic crystal waveguide (PCW). The waveguide is created by removing one row of holes in the nearest-neighbour direction of air holes placed on a triangular lattice with pitch Lambda=380 nm in a silicon-on-insulator (SOI) material

Photonic wire splitters have been designed using topology optimization. The splitters have been fabricated in silicon-on-insulator material and display broadband low-loss 3 dB splitting in a bandwidth larger than 100 nm.

We demonstrate a nanoimprint process for fabrication of photonic crystal devices. The nanoimprint process, defining stamp patterns in a thin e-beam resist, yields improved pattern replication compared to direct e-beam writing of the devices.

The crystal structure in a silicon waveguide can be distorted by application of strain. Thereby, the otherwise forbidden linear electrooptic (Pockels) effect is induced, opening a new route for optical modulation in silicon.

We report on transmission, field mapping, and spectral dependence of the group index in the slow light regime, obtained by numerical modelling. The influence of a finite number of lattice periods on the observed properties is pointed out.

We demonstrate a concept for tailoring the group velocity and dispersion properties for light propagating in a planar photonic crystal waveguide. By perturbing the holes adjacent to the waveguide core it is possible to increase the useful bandwidth below the light-line and obtain a photonic crystal waveguide with either vanishing, positive, or negative group velocity dispersion and semi-slow light. We realize experimentally a silicon-on-insulator photonic crystal waveguide having nearly constant group velocity [similar to]c$-0$//34 in an 11-nm bandwidth below the silica-line. $CPY@2006 Optical Society of America.

We report on direct numerical calculations and experimental measurements of the group-index dispersion in a photonic crystal waveguide fabricated in silicon-on-insulator material. The photonic crystal is defined by a triangular arrangement of holes and the waveguide is carved out by introducing a one-row line defect. Both the numerical and experimental methods are based on the time of flight approach for an optical pulse. An increase of the group index by approximately 45 times (from 4 to 155) has been observed when approaching the cutoff of the fundamental photonic bandgap mode. Numerical 2D and 3D simulations of pulse dynamics in the waveguide made by the time-domain method shows excellent agreement with measured data in most of the band. These group index values in a photonic crystal waveguide are to the best of our knowledge the largest numbers reported so far by direct tracking of pulse propagation.

A silicon-on-insulator photonic crystal waveguide is tailored to obtain a ~20-nm low-loss bandwidth with low group-index dispersion and group velocity around c/20. This is obtained by perturbing the holes adjacent to the waveguide core.

Nano-photonic technologies of GaAs-based two-dimensional photonic crystal (2DPC) slab waveguides and InAs-based quantum dots (QDs) are reviewed for a symmetric Mach-Zehnder type, ultra-small and ultra-fast all-optical switch (PC-SMZ) and new logic (PC-FF) device.

The topology optimization method has been used to improve the coupling into the slow light wavelength regime in planar photonic crystal waveguides. The coupling efficiency has been enhanced by more than 5 dB.

We apply the antiresonant reflecting layers arrangement to silicon-on-insulator based photonic crystal waveguides. Several layered structures with different combinations of materials (Si-SiO/sub 2/, Si/sub 3/N/sub 4/-SiO/sub 2/) and layer topology have been analysed. Numerical modelling using the 3D finite-difference time-domain method reveals promising low-loss results with potential for competing with membrane-like photonic crystal waveguides.

We present examples of ultra-compact photonic crystal components realized in silicon-on-insulator material. We have fabricated several different types of photonic crystal waveguide components displaying high transmission features. This includes 60/spl deg/ and 120/spl deg/ bends, different types of couplers, and splitters. Recently, we have designed and fabricated components with more than 200 nm bandwidths. Design strategies to enhance the performance include systematic variation of design parameters using finite-difference time-domain simulations and inverse design methods such as topology optimization.

A scanning near-field optical microscope is used to directly map the propagation of light in the wavelength range of 1500-1630 nm along straight photonic crystal waveguides (PCWs) fabricated on silicon-on-insulator wafers. The PVWs were formed by removing a single row of holes in the triangular 428-nm-period lattices with different filling factors (0.76 and 0.82) and connected to access ridge waveguides. Using the near-field optical images we investigate the light propagation along PCWs for TM and TE polarization (the electric field is perpendicular/parallel to the sample surface). Efficient guiding (for both samples) of the TM-polarized radiation is observed in the whole range of laser tunability. For TE polarization, the efficient guiding is limited to the wavelengths shorter than 1552 or 1570 nm for the PCW with the filling factor of 0.76 or 0.82, respectively. For longer wavelengths, we observe drastic and rapid deterioration of the waveguiding and PCW mode confinement, ending up with the complete disappearance of the PCW mode once the wavelength exceeds the cutoff value by merely 2 nm. Using averaged cross sections of the intensity distributions along the PCW axis, the propagation loss is evaluated and found to be in good agreement with the corresponding transmission spectra. Considering spatial frequency spectra of the intensity variations along the PCW axis, we determine (for both polarizations) the dispersion of the PCW mode propagation constant and, thereby, the mode group and phase velocities.

Topology optimization was used to design a planar photonic crystal waveguide 60/spl deg/ bend leading to a record-breaking transmission bandwidth of more than 200 nm. The experimental results agree well with 3D finite-difference-time-domain simulations.

A scanning near-field optical microscope (SNOM) is used to directly map the propagation of light in a specially designed 50/50 photonic crystal (PC) Y-splitter fabricated on silicon-on-insulator (SOI) wafers. SNOM images are obtained for TE- and TM-polarized light in the wavelength range 1425–1570 nm. The recorded intensity distributions exhibit highly wavelength (and polarization) dependent intensity variations along the propagation direction, especially around the fork and bend regions. By comparing the SNOM images recorded in and after the PC Y-splitter area, the features of light distribution are analysed for both polarizations. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We have designed and fabricated a novel 90/spl deg/ bend in a photonic crystal waveguide. The design was obtained using topology optimization and the fabricated waveguide displays a bend loss for transverse-electric-polarized light of less than 1 dB per bend in a 200-nm wavelength range.

The paper reports on the measurement and evaluation of the group velocity (GV) dispersion in the proximity of the cutoff wavelength for the fundamental photonic bandgap mode in a 2D photonic crystal waveguide (PCW). The PCW is created by introducing a line defect in an otherwise perfect triangular lattice of air-holes in the 216-nm thick silicon layer in an SOI material. Experimental transmission spectra show a mode cut-off around 1562.5 nm for the fundamental photonic bandgap mode. In order to measure and model the group index of modes in the PCW, a time-of-flight (ToF) method is applied.

We demonstrate a new device concept for wavelength division demultiplexing based on planar photonic crystal waveguides. The filtering of wavelength channels is realized by shifting the cutoff frequency of the fundamental photonic bandgap mode in consecutive sections of the waveguide. The shift is realized by modifying the size of the border holes. Simulations and an experimental realization of a four-channel coarse wavelength division demultiplexer are described.