Abstract
Ribbon plastic optical fiber (POF) linked four-channel optical transmitter (Tx) and receiver (Rx) modules have been proposed and realized featuring an excellent alignment tolerance. The two modules share a common configuration involving an optical sub-assembly (OSA) with vertical cavity surface emitting lasers (VCSELs)/photodetectors (PDs), and their driver ICs, which are integrated onto a single printed circuit board (PCB) substrate. The OSA includes an alignment structure, a beam router and a fiber guide, which were produced by using plastic injection molding. We have accomplished a fully passive alignment between the VCSELs/PDs and the ribbon POF by taking advantage of the alignment structure that serves as a reference during the alignment of the constituent parts of the OSA. The electrical link, which largely determines the operation speed, has been remarkably shortened, due to a direct wire-bonding between the VCSELs/PDs and the driver circuits. The light sources and the detectors can be individually positioned, thereby overcoming the pitch limitations of the ribbon POF, which is made up of perfluorinated graded-index (GI) POF with a 62.5 μm core diameter. The overall alignment tolerance was first assessed by observing the optical coupling efficiency in terms of VCSEL/PD misalignment. The horizontal and vertical 3-dB alignment tolerances were about 20 μm and 150 μm for the Tx and 50 μm and over 200 μm for the Rx, respectively. The VCSEL-to-POF coupling loss for the Tx and the POF-to-PD loss for the Rx were 3.25 dB and 1.35 dB at a wavelength of 850 nm, respectively. Subsequently, a high-speed signal at 3.2 Gb/s was satisfactorily delivered via the Tx and Rx modules over a temperature range of -30 to 70°C with no significant errors; the channel crosstalk was below -30 dB. Finally, the performance of the prepared modules was verified by transmitting a 1080p HDMI video supplied by a Bluelay player to an LCD TV.
Highlights
In response to the explosively growing demands for high-capacity video/data transmission capability, optical interconnects have drawn ample attention as a viable alternative to conventional copper based electrical interconnects due to their salient features: a low power consumption, a light weight, immunity to electromagnetic interference, and a short signal delay time [1,2]
Considering that the optical coupling between the optoelectronic devices and the plastic optical fiber (POF) is the most critical for an optical sub-assembly (OSA), we have mainly focused on the alignment tolerance of the vertical cavity surface emitting lasers (VCSELs)/PDs, the VCSEL-to-POF coupling, the POF-to-PD coupling, and the channel crosstalk, for the design of the transmit OSA (TOSA) and the receive OSA (ROSA)
The beam router and the fiber guide are subsequently self-aligned to the alignment structure, so that the ribbon POF is aligned to the VCSELs/PDs in a natural way
Summary
In response to the explosively growing demands for high-capacity video/data transmission capability, optical interconnects have drawn ample attention as a viable alternative to conventional copper based electrical interconnects due to their salient features: a low power consumption, a light weight, immunity to electromagnetic interference, and a short signal delay time [1,2]. Transmitter (Tx) and receiver (Rx) modules, requiring a low cost and a large volume production capability, are suitable to the adoption of optical interconnects [4,5,6,7,8] Toward this end, an optical sub-assembly (OSA) using vertical cavity surface emitting lasers (VCSELs) has been extensively studied [4,8,9,10,11,12], in conjunction with plastic optical fibers (POFs) allowing for an easy handling [4,5,12]. The pitch for the ribbon POF may be customized by mounting the VCSELs/PDs individually
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