Large-capacity Optical Communication Systems Research Articles

InP-based Double-heterojunction Bipolar Transistors for Large-capacity Optical Communication Systems

InP-based Double-heterojunction Bipolar Transistors for Large-capacity Optical Communication Systems

Mode division (de)multiplexer based on transverse mode conversion in photonic crystal using asymmetric directional couplers.

Mode division multiplexing technology has the potential to increase the channel capacity of a single wavelength carrier. Attaining cost-effective high-bandwidth-density devices with small footprints is a concern, and photonic crystal based devices are promising for ultra-small on-chip communications. This paper presents a 2D photonic crystal based mode division (de)multiplexer on a silicon on insulator platform. The device comprises two coupling regions of asymmetric directional couplers that perform mode conversion operations between the fundamental mode and higher-order modes. Each coupling section is dedicated to converting a specific mode. Mode conversion is achieved by designing a multimode waveguide to satisfy the phase-matching condition of the desired mode with the single mode waveguide. Two linear adiabatic tapers are introduced for the smooth transition of modes between waveguide sections. The device is designed and simulated for three-channel modes at 1550nm using the finite-difference time-domain technique. The obtained insertion loss and cross talk are <0.41d B and <-20.14d B, respectively. The overall size of the proposed mode division (de)multiplexer is 328.5µm 2. A fabrication tolerance study for the proposed device is performed by varying the rod radius and position in the device structure's taper and bus waveguide regions. The proposed 2D photonic crystal based mode division (de)multiplexer has the potential to be used in large-capacity optical communication systems.

Design and fabrication optimization of low-crosstalk silicon arrayed waveguide gratings with 32 channels and 100-GHz spacing

To satisfy the stringent requirements of large-capacity optical communication systems, the high-performance silicon arrayed waveguide gratings (AWG) with 32 wavelength channels and 100 GHz spacing are designed and fabricated. First of all, three types of arrayed waveguides are designed for seeking better performances, including rectangular-type, arc-type, and S-type ones. During fabrication, the taper connector is then introduced and the waveguide sidewall is further smoothed. Among the samples fabricated using E-beam lithography (EBL), the one with rectangular-type arrayed waveguides is characterized with better performance, showing a crosstalk of −14 dB and an insertion loss of 7.5 dB. Then, the target design with rectangle arrayed waveguides is further optimized and fabricated using 180-nm lithography platform for massive production. Outstanding results are achieved with an insertion loss of 4.5 dB, a channel uniformity of 0.95 dB, and a crosstalk as low as −20.4 dB, respectively. As far as we know, the AWGs might be the first compact silicon one fabricated by commercial lithography platform, characterized by comprehensive specifications (i.e., lowest crosstalk, highest channel uniformity, lowest insertion loss) for massive 100-GHz wavelength multiplexing/de-multiplexing.

An integrated device for electro-optic modulation and dense wavelength division multiplexing based on photonic crystals

We proposed an integrated device for electro-optic (EO) modulation and dense wavelength division multiplexing (DWDM) based on photonic crystals (PhCs). The transmittance performance of the designed structure was modelled and analyzed according to the time-domain coupled mode theory (CMT), using three-dimensional finite-difference time-domain (3D-FDTD) method to calculate the parameters of the proposed device for verification. The numerical results show that the proposed integrated device can realize the functions of “on”, “off” modulation and DWDM with a channel spacing of 0.8 nm at the operating wavelengths of 1555 nm and 1554.2 nm. The minimum insertion loss, channel crosstalk and modulation voltage are 0.7 dB, − 29.04 dB and 0.88 V, respectively. The maximum extinction ratio and modulation speed are 21.51 dB and 29.4 GHz. The designed integrated device has the advantages of low loss, compact size (41.28μm×11.18μm), narrow channel spacing, large extinction ratio, which can be easily expanded the number of channels and used in highly integrated large-capacity optical communication systems and data center.

Design and Analysis of Trench-Assisted Low-Bending-Loss Large-Mode-Field-Area Multi-Core Fiber with an Air Hole

In this paper, a trench-assisted low-bending-loss large-mode-field-area multi-core fiber with air hole is proposed, which can achieve dual-mode transmission. The influence of structural parameters on fiber performance is analyzed systematically, and the structure of the trench, with a lower refractive index than the cladding, is also analyzed and optimized. By adjusting the structural parameters, the effective mode field area of the fundamental mode can reach 2003.24 um2 at 1550 nm, and when the bending radius is 1 cm, the bending loss is 2.57 × 10−3 dB/m. The practical implementation of the proposed fiber is feasible using existing fabrication technology and is applicable to the transmission of large-capacity optical communication systems and high-power lasers.

A hybrid multiplexer/de-multiplexer for wavelength-mode-division based on photonic crystals

A hybrid multiplexer/de-multiplexer (HMUX/HDeMUX) for wavelength-mode-division based on photonic crystals (PCs) is presented. The proposed device consists of a point-defect cavity, a wavelength-selective cavity and asymmetrical parallel waveguides. Coupled-mode theory (CMT) is applied to the analysis, and the finite-difference time-domain (FDTD) method is used for the simulations. The simulation results show that the device can multiplex the fundamental and first-order modes of 1550 and 1310 nm. It exhibits not only a low insertion loss (<0.37 dB) but also low mode crosstalk (<−13 dB). Thus, the PC-based HMUX/HDeMUX has considerable potential for application in large-capacity optical communication systems.

Dispersion compensation optical fiber modules for 40 Gbps WDM communication systems

Dispersion compensation was originally proposed to equalize pulse distortion. With the development of wavelength division multiplexing (WDM) techniques for large capacity optical communication systems, dispersion compensation technologies have been applied into the field. Fiber-based dispersion compensation is an attractive technology for upgrading WDM communication systems because of its dispersion characteristics and good compatibility with transmission optical fibers. Dispersion compensation fibers and the modules are promising technologies, so they have been receiving more and more attention in recent years.

Dispersion-flattened Bragg photonic crystal fiber for large capacity optical communication system

A novelty dispersion ultra-flattened Bragg photonic crystal fiber (PCF) has been fabricated in this paper. The fiber is composed of compound cores and periodical claddings with 11 coaxial rings. It has flattened dispersion of 8.5±1.3 ps·(nm·km)−1 in the communication wavelength range of 1460–1625 nm. Its dispersion slope alters from −0.0428 to 0.0392 ps·nm−2·km−1. The low attenuation of 0.52 dB/km and low bending loss of 0.09 dB at 1550 nm of the fiber are also achieved. The Bragg PCF has enormously potential application in the fields of dense wavelength division multiplexing systems because of its superior dispersion properties and easy splicing performances.

Trend of Ultrafast Optical Device and Laser Technologies.

Optical Time Division Multiplexing (OTDM) is attracting much attention for use in future largecapacity optical communication systems. In such systems, optical pulses with short pulse width, high repetition rate, low timing jitter, and low chirp, are required. This paper reviews ultrafast optical pulse sources, such as modelocked semiconductor lasers, electroabsorption modulators, and mode-locked fiber lasers.

OTDM communication system exploiting a modelocked fiber laser as the clock extractor

This paper briefly describes the WDM and OTDM techniques in large capacity and super large capacity optical communication systems. We propose a novel method of employing a modelocked fiber laser as the clock extractor in communication systems, and present the structure for a totally new all optical OTDM experimental communication system that is based on the use of a wavelength division prescaled clock pulse scheme.