Multimode polymer waveguides have been developed to create low-cost, high-speed on-board optical interconnects. Buried optical waveguides made from SU-8 in a polymethyl methacrylate polymer (PMMA) substrate covered with a thin PMMA sheet are a low-cost option for electro-optical interconnects. The propagation losses for a 600  μm×600  μm straight waveguide were 1.96, 1.32, and 1.39  dB/cm, respectively, at three different wavelengths (850, 1310, and 1550 nm). The bending loss for a 15 mm bending radius is as high as 6  dB/cm. Transition and radiation losses dominate overall loss when the bending radius is less than 30 mm. The waveguide was excited using a multimode 850 nm VCSEL transmitter and detected using butt-coupled and lens-coupled receivers. The coupling loss was about 1 dB for the butt-coupling technique and 2 dB for lens coupling. The response bandwidth and the group delay of direct modulated (IF) signal were independent of the channel waveguide for communication speeds up to more than 3 GHz. This technique is viable for low-cost, short-length buried optical waveguides.

A simple and cost-effective technology to integrate an optical waveguide into circuits in plastic board has been used to develop a 0.6 3 0.6 mm 2 polymer waveguide in a plastic substrate. A simple direct coupling method was used to couple the light from a multimode optical fiber to the SU-8 waveguide core. The interconnect achieved 2.45 and 2.54 dB/cm propagation loss at 1550 nm and 1310 nm wavelength, respectively, for a polyvinyl chloride polymer cladding and 1.66 and 1.51 dB/cm at 1550 and 1310 nm wavelength, respectively, for polymethyl methacrylate polymer cladding.

Electro-optical circuit boards should provide simple and cost-effective coupling techniques and crosstalk levels of less than -30  dB. A dicing saw was used to create waveguide grooves with a surface roughness of less than 183 nm in a 1.6-mm-thick polymethyl methacrylate polymer (PMMA) substrate. The buried optical waveguides were made from SU-8 in a PMMA substrate covered with a 1-mm PMMA sheet. The propagation loss for a 500  μm×570  μm straight waveguide was 0.9 dB/cm at 1310 nm. The coupling between parallel waveguides was measured at separation distances from 45 to 595 μm. The crosstalk was less than -40  dB for 65-mm-long waveguides. This fabrication method shows potential for dense optical interconnects with very low crosstalk.

Temperature controlled food transport is essential for human safety and to minimise food waste. The thermal properties of food are important for determining the heat transfer during the transient stages of transportation (door opening during loading and unloading processes). For example, the temperature of most dairy products must be confined to a very narrow range (3-7˚C). If a predefined critical temperature is exceeded, the food is defined as spoiled and unfit for human consumption. An improved empirical model for the thermal conductivity and specific heat capacity of a wide range of food products was derived based on the food composition (moisture, fat, protein, carbohydrate and ash). The models that developed using linear regression analysis were compared with the published measured parameters in addition to previously published theoretical and empirical models. It was found that the maximum variation in the predicated thermal properties leads to less than 0.3˚C temperature change. The correlation coefficient for these models was 0.96. The t-Stat test (P-value > 0.99) demonstrated that the model results are an improvement on previous works. The transient heat transfer based on the food composition and the temperature boundary conditions was found for a Camembert cheese (short cylindrical shape) using a multiple dimension finite difference method code. The result was verified using the heat transfer today (HTT) educational software which is based on finite volume method. The core temperature rises from the initial temperature (2.7˚C) to the maximum safe temperature in ambient air (20.24˚C) was predicted to within about 35.4±0.5 minutes. The simulation results agree very well (+0.2˚C) with the measured temperature data. This improved model impacts on temperature estimation during loading and unloading the trucks and provides a clear direction for temperature control in all refrigerated transport applications.

Buried optical interconnects promise high speed 1 interconnections between electronic circuits on circuit boards. 2 Previous attempts have relied on expensive microfabrication 3 technologies and complex optical coupling systems. The circuits 4 in plastic (CiP) manufacturing method has electronic compo-5 nents embedded in a plastic substrate making direct optical 6 coupling possible. Four different machining methods were used to 7 create optical waveguides in polymethyl methacrylate (PMMA) 8 substrate and with SU8 channel, covered with a thin sheet of 9 PMMA. A three-layer milling technique showed least attenuation 10 (1.17 and 1.20 dB/cm at 1310 and 1550 nm, respectively). The 11 technique shows significant promise for low cost fabrication of 12 CiP with optical interconnects. 13 Index Terms-Circuits in plastic (CiP), CNC milling, hot 14 embossing, optical interconnects, optical waveguides. 15 I. INTRODUCTION AND BACKGROUND 16 O PTICAL communications offer high data rates over 17 long distance links for intercontinental and local area 18 networks. For short distance applications (less than 1m) 19 multimode optical interconnects have been used to connect 20 semiconductor devices on circuit boards and between circuit 21 boards. Multimode waveguides are relatively simple to fabri-22 cate and coupling precision is not critical when compared to 23 single mode waveguides. Researchers [1]-[4] have replaced 24 electrical with optical paths to achieve increased data trans-25 fer speeds between digital circuits. Optical interconnects are 26 not susceptible to radio frequency interference and earthing 27 problems. Other advantages include voltage isolation, reduced 28 power dissipation and minimal crosstalk. 29 Polymer waveguides have been used as alternatives to 30 embedded fibers to achieve higher data rate, density, coupling 31 efficiency and lower cost. Polymer materials were found to be 32 the best candidate to fabricate the waveguide for their favor-33 able properties such as, compatibility with standard printed 34 circuits, low cost, high temperature stability, and low loss 35