Abstract
A 40 Gb/s bidirectional optical link using four-channel optical subassembly (OSA) modules and two different wavelengths for the up- and down-link is demonstrated. Widely separated wavelengths of 850 nm and 1060 nm are used to reduce the optical crosstalk between the up- and down-link signals. Due to the integration capabilities of silicon, the OSA is implemented, all based on silicon: V-grooved silicon substrates to embed fibers and silicon optical benches (SiOBs) to mount optical components. The SiOBs are separately prepared for array chips of photodiodes (PDs), vertical-cavity surface-emitting lasers (VCSELs), and monitoring PDs, which are serially configured on an optical fiber array for direct coupling to the transmission fibers. The separation of the up- and down-link wavelengths is implemented using a wavelength-filtering 45° mirror which is formed in the fiber under the VCSEL. To guide the light signal to the PD another 45° mirror is formed at the end of the fiber. The fabricated bidirectional OSA module shows good performances with a clear eye-diagram and a BER of less than 10(-12) at a data rate of 10 Gb/s for each of the channels with input powers of -8 dBm and -6.5 dBm for the up-link and the down-link, respectively. The measured inter-channel crosstalk of the bidirectional 40 Gb/s optical link is about -22.6 dB, while the full-duplex operation mode demonstrates negligible crosstalk between the up- and down-link.
Highlights
Optical interconnections are utilized to meet the increased level of demand pertaining to internet data traffic and to overcome the limitations of electrical interconnects due to advantages such as a short signal delay, a light weight, lower power consumption, and immunity to electromagnetic interference [1,2,3]
These vertical-cavity surface-emitting lasers (VCSELs), PD and M-PD silicon optical benches (SiOBs) are attached onto an optical fiber array embedded in a V-groove which is formed in a silicon substrate
Two different modules for the up-link to send 850 nm signals and for the downlink to send 1060 nm signals are installed on the same evaluation boards. These modules were connected using an OM3 standard multi-mode fiber (MMF) fibers array with four channels and a length of 2 m to measure the end-to-end optical link
Summary
Optical interconnections are utilized to meet the increased level of demand pertaining to internet data traffic and to overcome the limitations of electrical interconnects due to advantages such as a short signal delay, a light weight, lower power consumption, and immunity to electromagnetic interference [1,2,3]. Optical interconnects improve the speed and quality of data transmissions in short-reach applications such as data processing units, optical storage applications and in data centers. The high-storage data processing units of data centers require high-speed data transmission for rack-to-rack, board-to-board and chip-to-chip interconnections, with a design of high-capacity and compact pluggable optical modules for bidirectional optical links. Half-duplex bidirectional transmission can be implemented through a single fiber [4] or through two fibers [5]. Full-duplex bidirectional transmission has been implemented through two fibers [1]. In half-duplex optical interconnect applications, the bandwidth of the bidirectional data transmission is reduced, while in full-duplex data transmission, the efficiency is increased by simultaneous data transmission. Implementation of the full-duplex mode with two fibers increases the number of fibers for bidirectional transmission. In the proposed bidirectional optical link, we use different wavelengths for the up- and down-link to reduce the optical crosstalk between the up- and down-link through a single fiber
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