Abstract
We fabricate graded index (GI) multi-channel polymer optical waveguides comprised of poly methyl methacrylate (PMMA)-poly benzyl methacrylate copolymer for the purpose of achieving high thermal stability in the GI profiles. The waveguides obtained show slightly higher propagation loss (0.033 dB/cm at 850 nm) than doped PMMA based GI-core polymer waveguides we have reported, due to the excess scattering loss inherent to the mixture of copolymer and homo-polymer in the core area. In this paper, we focus on the influence of the excess scattering loss on mode conversion and inter-channel crosstalk. We simulate the behavior of light propagating inside the core with and without the scattering effect. Using the simulation, the excess loss experimentally observed in the copolymer-core waveguide is successfully reproduced, and then, we find that the excess scattering loss of 0.008 dB/cm could increase the inter-channel crosstalk from -30 dB to -23 dB which agrees with the experimentally observed value. Although the simulation of the inter-channel crosstalk was performed only on our GI-core polymer optical waveguides, it is capable of modeling the conventional SI rectangular-core waveguides. Some amount of excess scattering is generally observed in the conventional SI-core waveguides, and thus, the application of this simulation to SI-core waveguides allows a feasible design for high-density alignment of the waveguides.
Highlights
Multimode and multi-channel polymer optical waveguides have been expected to be high performance data communication devices for short range interconnections, ranging from onboard to board-to-board [1,2]
In order to address these problems, we have proposed to apply graded-index (GI) core polymer optical waveguides to such an on-board interconnection application [6,7]
In order to increase the thermal stability of the graded index (GI)-core polymer optical waveguides, we need to substitute the poly methyl methacrylate (PMMA) for other polymer materials with a high glass transition temperature, while it could have higher excess scattering loss
Summary
Multimode and multi-channel polymer optical waveguides have been expected to be high performance data communication devices for short range interconnections, ranging from onboard to board-to-board [1,2]. The propagation loss would be 0.1 dB/cm or higher except for some state-of-the-art ones [1,2], due to the excess scattering and absorption losses inherent to the polymer material Even for such on-board polymer optical waveguides, much higher channel data rates and density are required in the past few years [1], and current trends of polymer waveguide design are in smaller core size (~35 μm) and narrower inter-core pitch (~65 μm). In order to increase the thermal stability of the GI-core polymer optical waveguides, we need to substitute the PMMA for other polymer materials with a high glass transition temperature, while it could have higher excess scattering loss. This allows us to find the relationship among the light scattering, mode conversion and interchannel crosstalk quantitatively
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