Abang Annuar Ehsan

Variable coupling ratio Y-Branch plastic Optical fiber (POF) coupler with suspended waveguide taper

A variable coupling ratio Y-Branch plastic optical flber (POF) coupler based on acrylic has been developed. This device utilized two optical designs: a Y-branch structure with a novel suspended waveguide taper and a simple attenuation technique based on lateral displacement of two flbers for the non-symmetrical coupling ratios. The high index contrast waveguide taper is constructed on the acrylic block itself where the area surrounding the waveguide taper has been designed in such a way that it is surrounded by an open air. A simple attenuation technique based on lateral displacement of two adjoining flbers for each of the two output ports has been proposed and presented for the non-symmetrical coupling ratios. Lateral displacement of the flber is set from 4.4mm down to 1.6mm for output flber 1 and 0.1mm to 1.0mm for output port 2. Numerical analysis has been done on the lateral displacement of the output flbers which shows the device is able to generate non-symmetrical coupling ratios. Device modeling has been performed using non-sequential ray tracing technique on the Y-branch coupler performing as a 3dB coupler with an excess loss of 1.84dB and a coupling ratio of 50 : 50. The designed coupling ratios vary from 1% to 45% for port 1 and 99% down to 55% for port 2 whereas in the simulated device, ratios vary from 7.65% to 39.85% for port 1 and from 92.35% down to 60.15% for port 2. Fabrication of the device is done by producing the device structures on an acrylic block using high speed CNC machining tool. The fabricated device has an excess loss of 5.85dB while the coupling ratios are 56.86% and 43.14% when operating as a 3dB coupler. In the

An interdigitated diffusion-based In(0.53)Ga(0.47)As lateral PIN photodiode

A novel 3D modeling of a lateral PIN photodiode (LPP) is presented utilizing In0.53Ga0.47As as the absorbing layer. The LPP has profound advantages compared to the vertical PIN photodiode (VPD) mainly due to the ease of fabrication where diffusion or ion implantation can be used to form the p+ and n+ wells in the absorbing layer. The device has an interdigitated electrode structure to maximize optical absorption. At a wavelength of 1550 nm, optical power of 5 Wcm-2 and 5 V reverse bias voltage, the device achieved responsivity of 0.5 A/W. The -3dB frequency response of the device was at 14 GHz and it is able to cater for 10 Gbit/s optical communication networks.

Acrylic-based Y-branch POF coupler for "do-it-yourself" next generation optical devices

Optical devices are components which require sophisticated equipment and technically skilled manpower for device fabrication and assembling and most of the production costs are on the device assembly. However, the next generation optical components may not be devices assembled at the production line but it will be based on the concept of do-it yourself optical devices. We proposed a simple low-cost acrylic-based Y-branch POF coupler which can be assembled easily by the end users themselves. The device is composed of three sections: an input POF waveguide, an intermediate adjustable hollow waveguide taper region and output POF waveguides. Low cost acrylic-based material has been used for the device material. A desktop high speed CNC engraver is utilized to produce the mold inserts used for the optical device. In addition to the engraved device structure, 4 holes are drilled at each corner to allow a top plate to be screwed on top and enclosed the device structure. Included with this POF coupler assembly kit will be the mold insert, top acrylic block, input and output POF fibers (cleaved and stripped with different stripping lengths) and connecting screws. The short POF fibers are inserted into the engraved slots at the input and output ports until the fibers are positioned just before or butt-coupled to each other. The assembling is completed when the top plate is positioned and the connecting screws are secured. The POF coupler has an average insertion loss of 5.8 ± 0.1 dB, excess loss of 2.8 dB and a good coupling ratio of 1:1.

16-channel arrayed waveguide grating (AWG) demultiplexer design on SOI wafer for application in CWDM-PON

Arrayed Waveguide Grating (AWG) functioning as a demultiplexer is designed on SOI platform with rib waveguide structure to be utilized in coarse wavelength division multiplexing-passive optical network (CWDM-PON) systems. Two design approaches; conventional and tapered configuration of AWG was developed with channel spacing of 20 nm that covers the standard transmission spectrum of CWDM ranging from 1311 nm to 1611 nm. The performance of insertion loss for tapered configuration offered the lowest insertion loss of 0.77 dB but the adjacent crosstalk gave non-significant relation for both designs. With average channel spacing of 20.4 nm, the nominal central wavelength of this design is close to the standard CWDM wavelength grid over 484 nm free spectrum range (FSR).

Modeling and Optimization of Three-Dimensional Interdigitated Lateral p-i-n Photodiodes Based on In0.53Ga0.47As Absorbers for Optical Communications

Access networks such as Fiber-to-the-Home based on passive optical networks (FTTH-PON) are experiencing a paradigm shift where these ‘last-mile’ networks are experiencing the need to provide converged services to the end-user at home. Triple-play services such as data and voice operating at the optical wavelength, ┣=1310 nm as well as video (┣=1550 nm) at a minimal speed of 2.5 Gbps are demanded to achieve an all-optical-network revolution (Kim, 2003; Lee & Choi 2007). It is estimated that in 2011, there will be 10.3 million FTTH households in the USA alone (Lee & Choi 2007). Thus, there arises a need to produce optical components which can be fabricated easily and in a cost-effective manner to cater for this ever-increasing demand. The development of interdigitated lateral p-i-n photodiodes (ILPP) based on In0.53Ga0.47As (InGaAs) absorption layer can be achieved using cheap and easy CMOS fabrication techniques such as diffusion and ion implantation. This can cater for the ever increasing demand of fiber-to-the home passive optical access networks (FTTH-PON) operating at a minimal speed of 2.5 Gb/s. The InGaAs ILPP which converts optical signals to electrical signals in the optical receiver has advantages compared to other photodiode structures because it has a high-resistance intrinsic region thus reducing Johnson noise, has low dark currents, permits a large detection area along with a low device capacitance, and can be monolithically integrated with planar waveguides or other devices. This chapter summarizes our key results on the modeling, characterization and optimization of ILPP based on In0.53Ga0.47As absorbers for optical communications. A three dimensional model of ILPP InGaAs operating at the optical wavelength, ┣ of 1.55 μm was developed using an industrial-based numerical software with a proposed fabrication methodology using spinon chemicals. New parameters for three different carrier transport models were developed and the proposed design was characterised for its dark and photo I-V, responsivity, -3dB frequency and signal-to-noise ratio (SNR) values. Statistical optimization of the InGaAs ILPP model was executed using fractional factorial design methodology. Seven model design factors were investigated and a new general linear model equation that relates the responsivity to significant factor terms was also developed (Menon, 2008; Menon et al.,2008a; Menon et al., 2008b; Menon et al. 2009)

Acrylic-based 1×2 Y-Branch POF coupler with high index contrast waveguide taper

An acrylic-based 1x2 Y-Branch POF coupler consists of input POF waveguide, a middle high index contrast waveguide taper and output POF waveguides has been developed. The optical device is based on a 1x2 Y-branch coupler design with a middle high index contrast waveguide taper. Device modeling has been performed using non-sequential ray tracing with an insertion loss of 4.68 dB and coupling ratio of 50:50. Low cost acrylic material has been used for the device substrate. This middle waveguide taper region is constructed on the acrylic block itself without using any additional optical waveguiding medium injected into the engraved taper region. Fabrication of the devices is done by producing the device structures on an acrylic block using high speed CNC machining tool. Input and output POF fibers are inserted in to this device structure in such a way that they are passively aligned to the middle waveguide taper structure. The measured insertion loss is 7.5 dB and with a splitting ratio of 50:50.

Dual pump configuration on oscillator of wavelength conversion on four wave mixing using PCF

The work presented here shows the effect of wavelength conversion experiment on Four Wave Mixing (FWM) by utilising photonic crystal fibre(PCF). This configuration consists of dual pump and a few sets of Fiber Bragg Gratings (FBGs). Selective conversion is also possible by adjusting on one of pump laser. However, phase matching conditions plays vital roles in this experiment. This phenomenon is the major cause of FWM.

Design and application of 8-channel SOI-based AWG demultiplexer for CWDM-system

Arrayed Waveguide Grating (AWG) serving as a demultiplexer (demux) has been designed on SOI platform and was utilized in a Coarse Wavelength Division Multiplexing (CWDM) system ranging from 1471 nm to 1611 nm. The investigation was carried out at device and system levels. At device level, 20 nm (∼ 2500 GHz) channel spacing was successfully simulated using beam propagation method (BPM) under TE mode polarization with a unique double S-shape pattern at arrays region. The performance of optical properties gave the low values of 0.96 dB dB for insertion loss and – 22.38 dB for optical crosstalk. AWG device was then successfully used as demultiplexer in CWDM system when 10 Gb/s data rate was applied in the system. Limitation of signal power due to attenuation and fiber dispersion detected by BER analyzer =10−9 of the system was compared with theoretical value. Hence, the maximum distance of optical fiber can be achieved.

Measurement of nonlinear refractive index based on multiple configuration of FBG in generating multi wavelength

A reliable method for measurement of the nonlinear refractive index through application of multi wavelength phenomenon. Multi wavelength realisation based on Erbium doped fibre laser (EDFL) is proposed and experimentally demonstrated. A combination of 15 m high efficiency Erbium doped fibre (EDF) and a 20 m Photonic Crystal Fibre (PCF) as main catalyst to suppress the homogenous broadening of EDF and to obtain highly stability of multi wavelength through insertion of a set of fibre Bragg gratings (FBGs) in the cavity. This PCF has zero dispersion of 1040 nm which mismatch from transmission window of 1550 nm. A reliable repeatability of multi wavelength based on multiple configuration of FBGs less than 0.2% obtained. This consistent results influence in determination of nonlinear refractive index by relation of four wave mixing (FWM).

Asymmetric hollow POF coupler design for portable optical access card system

An optical code generating device using plastic optical fiber (POF) coupler for portable optical access card system is presented. The code generating device constructed using asymmetric hollow POF coupler design provides a unique series of output light intensities which are successively used as an optical code. Each coupler will be assigned with a unique optical code based on the asymmetrical waveguide design. Non-sequential ray tracing simulation of various coupler designs showed a linear relationship between the tap-off ratio (TOFR) and the waveguide tap width. The results for the simulated and fabricated 1x2 asymmetric couplers show the same linear characteristics between the TOFR and the tap width. The simulated devices show a TOFR variation from 18.6% to 49.9% whereas the TOFR for the fabricated metal-based devices varies from 10.7% up to 47.7%, for a tap width of 500 μm to 1 mm. The insertion loss for the 1x2 asymmetric coupler at the tap line varies from 12.7 dB to 21.2 dB whereas for the bus line, the average insertion loss is about 12 dB.