We demonstrate direct bandwidth measurement of multimode polymer waveguides based on an optical sampling technique. The pulse shape can be completely recovered after transmission due to the advantages of optical sampling technology in the field of ultrashort pulse measurement. A reduction in averaged bandwidth (Bandwidth-length products) from 241 GHz (27 GHz·m) to 180 GHz (20 GHz·m) of 11 cm-long straight waveguides is observed when using mode scramblers (MS) to fully stimulate the higher-order modes. The effects such as bending, crossing, and twisting of both the rigid and flexible waveguides on the bandwidth are also investigated. The proposed method is effective for measuring the bandwidth and dispersions of waveguides, fibers and optical devices with a short length for varies applications.
This paper demonstrate a large-size directly inscribed optical waveguide for card-to-card optical interconnects applications. The waveguide was fabricated with commercially available UV-curable epoxies by combining use of a needle-type liquid micro-dispenser and a 3-axis robot stage known as the mosquito method. We designed and fabricated an “E” shaped waveguide device with 3 input/output ports and three connection routes with a length of about 21 cm, 21 cm, and 27 cm, respectively, to fit card-to-card connections of the optical backplane. The optical layout was designed to be scalable for conventional backplane sizes. Moreover, both the optical and geometrical parameters of the waveguides are designed to be compatible with commercial devices and can be terminated with MT connectors. The measurement results show good optical performance in insertion loss, crosstalk, misalignment tolerance, and good uniformity for all the 18 channels. The average insertion loss of the 27 cm-long channels is about 4.5 dB and the misalignment tolerance is larger than 20 μm for 3 dB loss penalty. The measured inter-channel waveguide crosstalk is lower than 42 dB. The waveguides also show excellent high-speed transmission performances with a NRZ signal at a data rate of 32 Gb/s. The experimental results imply that the large-size directly inscribed circular core polymer waveguide device is suitable for card-to-card optical interconnects applications and especially useful and versatile for the development of the porotype systems.
We introduce a universal test and measurement system allowing comparative characterisation of optical transceivers, board-to-board optical connectors and both embedded and passive optical circuit boards. The system comprises a test enclosure with interlocking and interchangeable test cards, allowing different technologies spanning different Technology Readiness Levels to be both characterised alone and in combination with other technologies. They form part of the open test design standards portfolio developed on the FP7 PhoxTroT and H2020 COSMICC projects and allow testing on a common test platform.
Pluggable optics are being pushed to their limits in terms of face plate density and power consumption requirements within emerging mega data centers and HPCs applications. Future applications seek silicon photonics based optical engines with ability for high channel count and throughput beyond 1Tb/s. In this paper, we show our results in development of single mode polymer-based optical-electrical PCBs (OEPCBs) supporting the emerging Si-Pho host PCB platforms with multi-terabit on-board routing capability for chip-to-chip communications. Single mode polymer waveguides (SM-PWGs) are fabricated using new photopatternable optical silicone materials (WG-2211/WG-2511-WG2711) on conventional PCBs. Test platform PCB shows designs with varying core sizes (20/15/12/9/7µm) and channel lengths (5-15cm). The measurements results show single-mode waveguides loss as less 0.4 dB/cm at 1310nm. Furthermore, the result show new waveguide material to be compliance for both rigid and flexible PCBs. OEPCB compliance evaluation test results shown in the paper includes results of lamination, chemical compliance, drilling, and plating tests. The results shown in the paper show first time ever fabrication of single mode polymer waveguide OEPCBs in production environment.
Widespread adoption of optical circuit boards will herald substantial performance, environmental and cost benefits for
the data communications industry. Though optical circuit board technology has advanced considerably over the past
decade, commercial maturity will be gated by the availability of conformity standards to forge future quality assurance
procedures. One important prerequisite to this is a reliable test and measurement definition system, which is agnostic to
the type of waveguide system under test and therefore can be applied to different optical circuit board technologies as
well as being adaptable to future variants. A serious and common problem with the measurement of optical waveguide
systems has been lack of proper definition of the measurement conditions for a given test regime, and consequently
strong inconsistencies ensue in the results of measurements by different parties on the same test sample. We report on the
development of a new measurement identification standard to force testers to capture sufficient information about the
measurement conditions for a given optical circuit board such as to ensure consistency of measurement results within an
acceptable margin. Furthermore we demonstrate how the application of the measurement identification system can bring
about a dramatic improvement in results consistency, by comparative evaluation of the results on multimode polymer
waveguide based optical circuit test boards from a large selection of testing organisations.
In this paper, we report developments of electro-optical PCBs (EO-PCB) with low-loss (<0.05dB/cm) polymer
waveguides. Our results shows successful fabrication of complex waveguide structures part of hybrid EO-PCBs utilizing
production scale process on standard board panels. Test patterns include 90° bends of varying radii (40mm – 2mm),
waveguide crossing with varied crossing angles (90°-20°), cascaded bends with varying radii, splitters and tapered
waveguides. Full ranges of geometric configurations are required to meet practical optical routing functions and layouts.
Moreover, we report results obtained to realize structures to integrate optical connectors with waveguides. Experimental
results are shown for MT in-plane and 90° out-of-plane optical connectors realized with coupling loss < 2dB and < 2.5
dB, respectively. These connectors are crucial to realize efficient light coupling from/to TX/RX chip-to-waveguide and
within waveguide-to-fiber connections in practical optical PCBs. Furthermore, we show results for fabricating electrical
interconnect structures e.g. tracing layers, vias, plated vias top/bottom and through optical layers. Process compatibility
with accepted practices and production scale up for high volumes are key concerns to meet the yield target and cost
efficiency. Results include waveguide characterization, transmission loss, misalignment tolerance, and effect of
lamination. Critical link metrics are reported.
Power consumption and scaling the performance and quantity of electrical interconnects for data traffic inside boards and backplanes are one of the critical barriers envisaged in next‐generation Data Center (DC) and High‐Performance Computing (HPC) applications. In this paper, we report developments of electro-optical PCBs (EO-PCB) with embedded polymer waveguide layers. We show results for fabricating realistic product emulator test vehicles that comprise of reasonable form factor PCBs with optical and electrical layers. The optical layer comprise of multiple waveguides exhibiting a full range of geometric configurations required to meet practical optical routing functions. Test patterns include varied cross-sectional sizes, 90° bends of varying radii (40mm – 2mm), cascaded bends with varying radii, waveguide crossings with varied crossing angles (90° - 20°), splitters, tapered waveguides and waveguide interconnect to midboard interface slots. Moreover, results for fabricating electrical interconnect structures (e.g. tracing layers, vias, plated vias) top/bottom and through optical layers in OE-PCB stack are shown. The purpose of the complex routed copper layers is to enable the crucial demonstration of the fabrication and thermal robustness challenges inherent to electro-optical PCBs with optical layers. Process compatibility with accepted practices and challenges in production scale up for high volumes are key concerns to meet the yield target and cost efficiency. Results include waveguide characterization, waveguide transmission loss, misalignment tolerance, and effect of lamination. Moreover, we show results on waveguide termination by in-plane edge connector and with 90° out-of-plane couplers.
A long-distance Optical Printed Circuit Boards (OPCB) was fabricated to realize high-speed optical interconnects. The OPCB was made up of polymer optical waveguides fabricated by using ultraviolet (UV) photolithography technique. The length of OPCB is 30cm. The minimal transmission loss of the optical waveguide is approximate 5.36dB at 850 nm wavelength. Two MT-RJ optical connecters were assembled on the OPCB to realize optical coupling between optical fibers and waveguides. The dependence of coupling loss on misalignment was obtained with different offset value theoretically and experimentally. The minimal total insertion loss is only 8.06dB. With 10 gigabits-per-second (Gbps) optical transceivers as the input/output module, we tested the performance of the OPCB. The date rate of 10Gbps can be transmitted successfully.
Technologies to design and fabricate high-bit-rate chip-to-chip optical interconnects on printed wiring boards (PWB) are studied. The aim is to interconnect surface-mounted component packages or modules using board-embedded optical waveguides. In order to demonstrate the developed technologies, a parallel optical interconnect was integrated on a standard FR4-based PWB. It consists of 4-channel BGA-mounted transmitter and receiver modules as well as of four polymer multimode waveguides fabricated on top of the PWB using lithographic patterning. The transmitters and receivers built on low-temperature co-fired ceramic (LTCC) substrates include flip-chip mounted VCSEL or photodiode array and 4x10 Gb/s driver or receiver IC. Two microlens arrays and a surface-mounted micro-mirror enable optical coupling between the optoelectronic device and the waveguide array. The optical alignment is based on the marks and
structures fabricated in both the LTCC and optical waveguide processes. The structures were optimized and studied by the use of optical tolerance analyses based on ray tracing. The characterized optical alignment tolerances are in the limits of the accuracy of the surface-mount technology.
Integration of high-speed parallel optical interconnects into printed wiring boards (PWB) is studied. The aim is a hybrid optical-electrical board including both electrical wiring and embedded polymer waveguides. Robust optical coupling between the waveguide and the emitter/detector should be achieved by the use of automated pick-and-place assembly. Different coupling schemes were analyzed by combining non-sequential ray tracing with Monte-Carlo tolerance simulation of misalignments. A modular demonstrator was designed based on three different kind of optical coupling schemes: butt-coupling and couplings based on microlens arrays and on micro ball lenses. The optical front-ends were implemented with PIN and flip-chip-VCSEL arrays as well as 10-Gb/s/channel electronics onto LTCC-based (low-temperature co-fired ceramic) transmitter and receiver modules, which were surface mounted on high-speed PWBs. An electrical simulation model was developed for the design of a VCSEL-based transmitter circuit. Polymer waveguides were fabricated on separate FR-4 boards to allow characterization of alignment tolerances with different waveguides. Optical and adhesion properties of several potential waveguide materials were characterized. The simulations and experiments suggest that, with optimized optomechanical structures and with low loss waveguides, it is possible to achieve acceptable total path loss and yield with the accuracy of automated assembly.
Integration of high-speed parallel optical interconnects into printed wiring boards (PWB) is studied. The aim is a hybrid optical-electrical board including both electrical wiring and embedded polymer waveguides. Robust optical coupling between the waveguide and the emitter/detector should be achieved by the use of automated pick-and-place assembly. Different coupling schemes were analyzed by combining non-sequential ray tracing with Monte-Carlo tolerance simulation of misalignments. The simulations demonstrate that, with optimized optomechanical structures and with very low loss waveguides, it is possible to achieve acceptable total path loss and yield with the accuracy of automated assembly. A technical demonstrator was designed and realized to allow testing of embedded interconnects based on three different kind of optical coupling schemes: butt-coupling, and couplings based on micro-lens arrays and on micro-ball lenses. They were implemented with PIN and flip-chip-VCSEL arrays as well as 10-Gb/s/channel electronics onto LTCC-based (low-temperature co-fired ceramic) transmitter and receiver modules, which were surface mounted on high-speed PWBs. The polymer waveguides were on separate FR-4 boards to allow testing and characterization of alignment tolerances with different waveguides. With micro-lens array transmitter, the measured tolerances (±10 μm) were dominated by the thickness of the waveguides.
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