Recent developments in the short distance communication have made polymer optical fibers (POF) an attractive product
in the high speed data communication market. The requirement of a large bandwidth, low cost, light weight and
flexibility in installation have placed them over the copper cables especially in applications like home networking and
automotives. Since POFs are large core multimoded fibers, their band width is limited by intermodal dispersion. This
confines POFs application to low data rate short distance communications. Restrictive mode launchers (RML) and
higher order mode strippers placed in the data link helps to reduce the intermodal dispersion. The techniques used to
implement these signal conditioners should be simple and cost effective to keep POFs attractive in the short distance
communication. In this paper we explore the possibility of integrating the RML and mode stripping elements in the
transmitter and receiver package itself. The pre-designed optical signal conditioning elements are projected to get
molded in the plastic packages and are fiber plug in modules. This connector less package design, universal to any light
source proposes to enhance the data rate and is widely manufacturable at an ease of installation and low cost.
Polymer Optical Fiber (POF) optical modules are gaining momentum due to their applications in short distance
communications. POFs offer more flexibility for plug and play applications and provide cost advantages. They also offer
significant weight advantage in automotive and avionic networks. One of the most interesting field of application is
home networking. Low cost optical components are required, since cost is a major concern in local and home networks.
In this publication, a fast and easy to install, low cost solution for efficient light coupling in and out of Step Index- POF
is explored. The efficient coupling of light from a large core POF to a small area detector is the major challenge faced.
We simulated direct coupling, lens coupling and bend losses for step index POF using ZEMAX<sup>R</sup> optical simulation
software. Simulations show that a lensed fiber tip particularly at the receiver side improves the coupling efficiency. The
design is optimized for 85% coupling efficiency and explored the low cost fabrication method to implement it in the
system level. The two methods followed for lens fabrication is described here in detail. The fabricated fiber lenses are
characterized using a beam analyzer. The fabrication process was reiterated to optimize the lens performance. It is
observed that, the fabricated lenses converge the POF output spot size by one fourth, there by enabling a higher coupling
efficiency. This low cost method proves to be highly efficient and effective optical coupling scheme in POF
An optical sub-assembly of MUX/DEMUX where optical devices are hybrid-integrated on a silicon optical bench (SiOB)
using a low cost passive alignment method was reported. A tight tolerance of positional and tilting angular accuracy is
required for optical devices attachment in order to maximize the coupling efficiency. The critical positioning transverse
to the optical axis merely depends on the symmetry, and accuracy of the position and shape of trenches. Any inaccuracy
primarily affects the non-critical positioning, i.e., z-axis & θz, in the direction along the optical axis; misalignment
accumulated and causes undesired insertion loss. All the piece parts, i.e., mirror, thin-film filters (TFFs), ball lens, SiOB
etc., have a defined tolerance in their dimensions and surfaces which increases the challenge in achieving high placement
accuracy along the optical axis. The effects from these inherent inaccuracies of the position and shape of trenches and
piece parts could be minimized by improve the bottom flatness, and proper procedure selection. Misalignment at each
axis, e.g. x-, y-, z-, θx, θy & θz was characterized and its effect to the coupling efficiency was discussed.
In this paper, the optical design of 4-channel WDM Transmission Optical Subassemblies (TOSA)/Receiver Optical
Subassemblies (ROSA) is reported. The TOSA and ROSA are being developed for uncooled modules for CWDM
applications and are compatible with the SFP/SFF form factor TOSA and ROSA. The physical dimension of OSA
together with the electronic circuitries is limited to 10×6×5 mm<sup>3</sup>. The designs of TOSA and ROSA are employed using
four thin film filters (TFFs) to select the specific channel wavelength, four 500 μm ball lenses, one 2.5 mm ball lens and
a high reflection mirror using folded optical configuration. The optical elements are to be assembled on a SiOB, except
the 2.5 mm ball lens. The simulation results are used to estimate the required optical components assembly accuracy.
Based on the simulation results, the tolerance requirement for tilting the mirror and first thin film filter is approximately
± 0.2° for the longest optical path namely Channel 4.
In this study, a low-cost (with bare chips) and high (optical, electrical, and thermal) performance optoelectronic system with
a data rate of 10Gbps is designed and analyzed. This system consists of a rigid printed circuit board (PCB) made of FR4
material with an optical polymer waveguide, a vertical cavity surface emitted laser (VCSEL), a driver chip, a 16:1 serializer,
a photo-diode detector, a Trans-Impedance Amplifier (TIA), a 1:16 deserializer, and heat spreaders. The bare VCSEL, driver
chip, and serializer chip are stacked with wire bonds and then solder jointed on one end of the optical polymer waveguide on
the PCB via Cu posts. Similarly, the bare photo-diode detector, TIA chip, and deserializer chip are stacked with wire bonds
and then solder jointed on the other end of the waveguide on the PCB via Cu posts. Because the devices in the 3D stacking
system are made with different materials, the stresses due to the thermal expansion mismatch among various parts of the
system are determined.
Silicon Optical Bench (SiOB) is a popular solution for passive assembly of optical module. In order to realize an optical
transmitter or receiver module, it is necessary to integrate high frequency optoelectronic components such as signal
photodiodes (PD) or laser diodes (LD) onto the SiOB. In this way, the module's electrical and optical performances can
be further improved, and a higher degree of miniaturization can be achieved. The challenge for this integration is not
only on the assembly accuracy for the LD and PD, it required the design of low loss electrical interconnect at high
frequency. However, the standard silicon substrate used in the SiOB has a high electrical loss especially at high
frequency. This imposed a limitation on the electrical interconnection length between the optoelectronic components and
their I/O interfaces. It is proposed here to design the electrical interconnection using a layer of SiO<sub>2</sub> sandwiched between
two layers of metal layer. Simulations have demonstrated that by varying the thickness of the SiO<sub>2</sub> layer, an optimum
electrical performance can be achieved.
The high cost of optoelectronics components typically used for long-haul communication is prohibitive in the Fiber to
the Home (FTTH) and Passive Optical Networks (PONs). One method of cost reduction is through the reducing the cost
of the electronics in the transceiver and reducing the packaging cost. We report the development of low-cost 2.5-Gbps
optical transceiver for Gigabit Passive Optical Network (GPON) using CMOS driver ICs and chip-on-board assembly
method. We developed the Laser Diode Driver (LDD), Trans-impedance Amplifier (TIA), Limiting Amplifier (LA) and
the Clock and Data Recovery (CDR) using CMOS technology for short reach application and developed the burst mode
version of the ICs for PON applications. The ICs are designed in house and fabricated on a standard CMOS 8" wafer
with 0.18μm technology. The devices operate at 1.8V and are low power in nature, thus reducing the demand on power
dissipation. The transceiver consists of an un-cooled and direct modulated laser diode driven with a LDD, a high speed
PIN photo-diode with amplifier and CMOS ICs. The bare CMOS ICs are attached on a transceiver substrate that is
compliant with the small form-factor pluggable (SFP) package multisource agreement (MSA) and coupled to a 1310nm
FP laser TOSA and a PIN ROSA with LC connector. The integrated transceiver is characterized up to 2.5-Gbps. In this
publication, we present the detail of the module development, assembly methods and performance characterization at
A taper coupler with multimode input and single mode output is presented for coupling between edge emitting laser
diode and silicon waveguide. The tapered coupler structure is optimized and tolerance for laser diode placement is
studied. A typical coupling efficiency of -2dB is achieved from laser diode to silicon waveguide. With tolerance of +/-
4μm laterally or vertically, the variation of the coupling efficiency is about 3dB. The tolerance is large compared with
other methods. Tilting angle at laser diode and the small gap between tapered coupler and silicon waveguide also affect
the overall coupling. From our studies, horizontal and vertical offsets are more critical for laser diode placement in order
to have a good coupling. The new design can be applied to photonics packaging because it will make passive assembly
easier by having larger tolerance for packaging compared with the conventional method with lens.
There is an increasing demand for tunable lasers in telecommunications networks for test equipment, optical components
and other applications. In DWDM systems, multiple data streams propagate concurrently on a single mode fiber.
DWDM networks are based on a DFB lasers operating at a wavelength defined by ITU wavelength grid. Statistical
variations associated with the manufacture of DFB laser results in yield losses. Continuously tunable external lasers are
developed to overcome the limitations of DFB lasers. Various laser tuning mechanisms are being explored to provide
external cavity tunable lasers to provide a stable single mode output.
The packaged tunable laser source (TLS) for DWDM network also need to include several optical elements for isolation
and data modulation like collimator, focusing lens, fiber pigtail, a modulator and output fiber segment. In this
publication, we propose a novel semi integrated miniature high frequency tunable laser design based on Silicon Optical
Bench (SiOB) concept. One of the mirrors is a movable MEMS structure changing the optical path length. We propose
micro optical design between laser diode and the MEMS mirror for efficient optical coupling and side mode suppression.
We also present the compatibility between the optical coupling and MEMS actuation range. We present the coupling
efficiency results over the tuning range. We also propose a method of monitoring the output power of the tunable laser
using waveguide coupler structures which are integrated in the silicon wafer and method of packaging in a miniature
package compatible to the industry standard form factor.
A new method of coupling the light from a laser diode to a Single Mode Fiber (SMF) with large alignment tolerances
and without using coupling lenses is presented. A pseudo vertical tapered coupler is designed for light coupling between
laser diode and single mode fiber. It has a large input aperture which is about 100 times the size of the laser waveguide
cross-section. The tapered coupler provides single mode output and matches the mode size with the single mode fiber.
The tapered coupler is fabricated on a silicon optical bench and is located between the laser and the fiber through the
silicon micrfabrication process. The misalignment between the fiber and taper coupler can be very small since this is
controlled by high precision silicon optical bench patterning processes. The coupler relaxes the laser diode placement
accuracies and eliminates the need for a coupling lens. Design Studies showed that the tolerance between the laser diode
and taper coupler can be more than +/-5μm misalignment at x-y, and +/-0.5degree tilting angle tolerance and the
fabricated assembly results are encouraging with good placement tolerances and coupling efficiency. The laser to single
mode fiber coupling tolerances is greatly improved and passive alignment for laser and single mode fiber is realized. The
technology can be useful for multi channel optical assembly where significant device and process cost saving can be
achieved and is suitable for functional integration for silicon photonics.
A compact wavelength division multiplexing (WDM) module is designed using discrete micro optics
components assembled on silicon optical bench for multiple-channel transceivers. This design is optimized
for a 4-channel multiplexer (MUX) plus a 4-channel demultiplexer (DEMUX). In this design, the micro
optics components for the MUX and DEMUX are integrated, and the MUX and DEMUX share the same
space. This helps to minimize the number of components required and hence reduce the cost and size.
Therefore, the module is compact enough to be put in small standard packages (SFF/SFP).
We present a concise method for the design of arrayed waveguide gratings (AWGs) with a minimum number of arrayed waveguides and polarization independence. As an example to demonstrate the effectiveness of the proposed method, a 16×16 AWG using silica-based sol-gel material is optimally designed with the following practical specifications: central wavelength of 1.554 µm, channel spacing of 100 GHz or 0.8 nm, crosstalk between adjacent channels of <–30 dB, insertion loss of <3 dB, and nonuniform power level of the channels of <1.75 dB. We present, to our knowledge, for the first time, a simple criterion for determining the minimum number of arrayed waveguides with polarization independence. The criterion ensures that lights diffracted in the first slab are transferred into the second slab without loss of the image information. The criterion is perfectly verified by simulating the design of the AWG using a beam propagation method of analysis. In addition, the design procedure also allows the optimization of the parameters and structure of the AWG to achieve the required performance specifications.
The development of Optoelectronic components for communications is converging towards access networks where device cost makes a significant impact on the market acceptance. Thus, the device design engineer needs to input assembly, fabrication and process constraints into the design at an early stage. The present study is part of a Project on Packaging of Optical Components that IME, Singapore has initiated as part of an ongoing Electronics Packaging Research Consortium with industry partnership. In the present study, the coupling of optical radiation from a laser diode to optical fiber is simulated for a fiber optic transmitter component development project. Different optical configurations based on direct coupling, spherical ball lenses, integral lensed fibers and thermally expanded fibers are created within the commercially available transmitter package space. The effect of optical element variables on the placement tolerance is analyzed and will be reported. The effect of alignment tolerances on the optical coupling is analyzed. Simulation results are presented recommending realizable alignment and placement tolerances to develop a low cost short range link distance transmitter.
The development of optoelectronic components for gigabit Ethernet communications is converging towards access networks where the cost of device makes a significant impact on the market acceptance. Device fabrication and packaging cost have to be brought down with novel assembly and packaging methods. Singapore has established a reputation in semiconductor device development and fabrication with excellent process and packaging facilities. Institute of Microelectronics (IME) was founded in 1991 to add value to the Singapore electronics industry. IME is involved in the development of active and passive photonics components using Silicon and polymer materials. We present a brief report on the development activities taking place in the field of optical component packaging at IME in recent years. We present a review of our competence and some of the optical device packaging activities that are being undertaken.
The internet has been the mantra in last decade and digital convergence is the latest talk on the tech streets. Features that once clearly discerned a mobile phone from a PDA or a PDA from a laptop are being replaced with multi-functional overlapping features and there is a growing need for wireless access and interoperability. Infrared communications has been addressing these needs for quite some time. The technology has matured through standardization efforts of IrDA (Infrared Data Association) and is widely used in PDAs, mobile phones, laptops, printers and digital cameras to name a few. This paper explores some new application scenarios for an IrDA transceiver. The first part of the paper describes a reference architecture for using infrared wireless communication for MP3 file exchange and the various possible user models. The second part of the paper discusses various configurations for implementing an ambient light detection scheme using IrDA transceivers, to turn off the backlighting of a LCD panel of a PDA or mobile phone in the presence of ambient light. The third part of the paper discusses various techniques of enabling extended link distance operation of IrDA transceivers for toy and remote control applications.