Bidirectional Optical Subassembly Research Articles

4 channel × 10 Gb/s bidirectional optical subassembly using silicon optical bench with precise passive optical alignment.

We demonstrate an advanced structure for optical interconnect consisting of 4 channel × 10 Gb/s bidirectional optical subassembly (BOSA) formed using silicon optical bench (SiOB) with tapered fiber guiding holes (TFGHs) for precise and passive optical alignment of vertical-cavity surface-emitting laser (VCSEL)-to-multi mode fiber (MMF) and MMF-to-photodiode (PD). The co-planar waveguide (CPW) transmission line (Tline) was formed on the backside of silicon substrate to reduce the insertion loss of electrical data signal. The 4 channel VCSEL and PD array are attached at the end of CPW Tline using a flip-chip bonder and solder pad. The 12-channel ribbon fiber is simply inserted into the TFGHs of SiOB and is passively aligned to the VCSEL and PD in which no additional coupling optics are required. The fabricated BOSA shows high coupling efficiency and good performance with the clearly open eye patterns and a very low bit error rate of less than 10-12 order at a data rate of 10 Gb/s with a PRBS pattern of 231-1.

Demonstration of Time- and Wavelength-Division Multiplexed Passive Optical Network Based on VCSEL Array

© 2016 Sil-Gu Mun et al. 9 http://dx.doi.org/10.4218/etrij.16.0115.0044 We demonstrate a timeand wavelength-division multiplexed passive optical network system employing a vertical-cavity surface-emitting laser array–based optical line terminal transceiver and a tunable bidirectional optical subassembly–based optical network terminal transceiver. A packet error–free operation is achieved after a 40 km single-mode fiber bidirectional transmission. We also discuss an arrayed waveguide grating, a photo detector array based on complementary metal–oxide– semiconductor photonics technologies, and low-cost key devices for deployment in access networks.

40 Gb/s optical subassembly module for a multi-channel bidirectional optical link

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.

Physical Media Dependent Prototype for 10-Gigabit-Capable PON OLT

In this work, we study the physical layer solutions for 10-gigabit-capable passive optical networks (PONs), particularly for an optical link terminal (OLT) including a 10-Gbit/s electroabsorption modulated laser (EML) and a 2.5-Gbit/s burst mode receiver (BM-Rx) in a novel bidirectional optical subassembly (BOSA). As unique features, a bidirectional mini-flat package and a 9-pin TO package are developed for a 10-gigabit-capable PON OLT BOSA composed of a 1,577-nm EML and a 1,270-nm avalanche photodiode BM-Rx, including a single-chip burst mode integrated circuit that is integrated with a transimpedance and limiting amplifier. In the developed prototype, the 10-Gbit/s transmitter and 2.5-Gbit/s receiver characteristics are evaluated and compared with the physical media dependent (PMD) specifications in ITU-T G.987.2 for XG-PON1. By conducting the 10-Gbit/s downstream and 2.5-Gbit/s upstream transmission experiments, we verify that the developed 10-gigabit-capable PON PMD prototype can operate for extended network coverage of up to a 40-km fiber reach.

1/10 Gb/s single transistor-outline-CAN bidirectional optical subassembly for a passive optical network

We propose a novel, low-cost bidirectional optical subassembly (BOSA) that uses a single glass-sealed conventional transistor-outline (TO)-CAN package for passive optical network application. In this BOSA, optical transmitting and receiving functions are incorporated into a silicon optical bench and in a TO-CAN package, respectively. With these features, the optical and electrical crosstalk is efficiently suppressed. The single TO-CAN BOSA has an extinction ratio of 11.69 dB and output power of 2.93 dBm for 1.25 Gb/s operation. The penalty of optical dispersion is 1.2 dB after 20-km single-mode fiber transmission. The receiver sensitivity is less than −30 dBm at a bit error rate of 10−3 for 10.3 Gb/s operation and the signal crosstalk penalty of a single TO-CAN BOSA is 0.8 dB.

10Gb/s BOSA Employing Low-Cost TO CAN Package and Impedance Matching Circuits in Transmitter

By using impedance (Z) matching circuits in a low-cost transistor outline (TO) CAN package for a 10Gb/s transmitter, we achieve a cost-effective and small bidirectional optical subassembly (BOSA) with excellent optical transmission waveforms and a > 40% mask margin over a wide temperature range (-10 to 85°C). We describe a design for Z matching circuits and simulation results, and discuss the advantage of the cost-effective compensation technique.

Single package directly modulated laser bidirectional optical subassembly using a modified mini-dual-in-line package for 10 Gbps passive optical networks

A bidirectional optical subassembly comprised of a 2.5 Gbps distributed feedback (DFB) laser diode (LD) directly modulated laser transmitter and a 10 Gbps positive intrinsic negative photodiode receiver was developed for an optical network unit of a 10 Gbps passive optical network. Here, a low-cost mini-dual-in-line package was modified to contain whole components of a transmitter and receiver in a single space while satisfying the requirements of 10 Gbps micro-device package standards. The transmitter was fabricated to achieve high optical output power by placing a micro aspheric lens very close to the DFB LD and reducing the thermal resistance between an LD chip and heat sink to bring down the DFB LD chip temperature. As a result, the transmitter output power was 3.5 dB higher than a conventional transistor outline can BOSA due to a high optical coupling efficiency of more than 70% and a low thermal resistance for heat dissipation. The receiver sensitivity was −21 dBm at a bit error rate of 10−3 and the sensitivity penalty of the receiver due to signal crosstalk was less than 0.3 dB.

Miniaturized bidirectional optical subassembly using silicon optical bench with 45-deg micro-reflectors in short-reach 40-Gbit/s optical interconnects

The development of a 4-channel×10-Gbits/s optical interconnect module based on a silicon optical bench (SiOB) is presented. The 4-channel vertical-cavity surface-emitting laser (VCSEL) and photo diode (PD) arrays are flip-chip assembled onto the pedestals of SiOB using Au/Sn solder bumps to form an SiOB-based bi-directional optical sub-assembly (BOSA) configuration. The optical coupling of VCSEL-to-multi-mode fiber (MMF) and MMF-to-PD without adding coupled optics is -5.2 and -2 dB , respectively. The wide alignment tolerances of 1-dB power variation for the transmitting and receiver parts to be ± 15 μ m are achieved. The clearly open 10-Gbits/s eye patterns of transmitting part as well as the 10 -12 -order bit error rate (BER) at the receiving part verify the proposed SiOB-based module is suitable for the application of 4-channel×10-Gbits/s optical interconnects.

10-Gbps electroabsorptive modulated laser bidirectional optical subassembly using novel two-window flat package for passive optical network

A novel 10-Gbps bidirectional optical subassembly (BOSA) comprised of a 1577 nm electroabsorptive modulated laser (EML) transmitter optical subassembly (TOSA) and 1270 nm avalanche photodiode (APD) receiver optical subassembly (ROSA) was developed. Here, a 10-Gbps microdevice compatible two-window flat package was proposed to simplify the EML BOSA structure, considering both the mechanical reliability and cooling performance. As a result, an optical output power of 8 dBm was obtained due to a high optical coupling efficiency of 60%, an extinction ratio of 7 dB, and a dispersion penalty at 20 km transmission of less than 1.5 dB for the EML TOSA. The APD ROSA sensitivity was -21.5 dBm at a bit error rate (BER) of 10−12 and -27 dBm at a BER of 10−3 without forward error correction. In addition, the sensitivity penalty of the APD ROSA due to signal crosstalk was less than 1.2 dB.

Compact bidirectional optical subassembly vertically stacked with 1.25-Gbps transmitter and 10-Gbps receiver for passive optical networks

A compact bidirectional optical subassembly (BOSA) for a 1.25/10-Gbps passive optical network is developed. A vertically stacked 1.25-Gbps transmitter based on a silicon optical bench, and a 10-Gbps receiver based on a low temperature cofired ceramic are implemented to realize low-cost manufacturing and miniaturization for single package application. The proposed BOSA delivers an extinction ratio more than 10 dB at 1.25-Gbps modulation, optical output coupling efficiency is more than 60%, rise and fall time is under 300 ps, and the side mode suppression ratio is more than 35 dB for the transmitter part. For the receiver part, responsivity is more than 0.6 A/W, and sensitivity is lower than -17 dBm at a 10-Gbps bit error rate 10-12 and -21 dBm at BER 10-3 without forward error correction. The cross talk between receiver and transmitter is less than -53 dB up to 10 GHz, and optical isolation is 33 dB.

Low-cost coaxial-type single TO-can bidirectional optical subassembly

A novel low-cost coaxial-type single transistor outline-can (TO-can) bidirectional optical subassembly (BOSA) using an all passive alignment BOSA platform and only one typical glass-sealed TO-can package is presented. This proposed BOSA platform is sufficiently compact to integrate in a single TO-can package and realises the reduction in cost by simplifying packaging processes. The measurement results of 3 dB bandwidth of the proposed single TO-can BOSA are 10.3 GHz for transmitter part and 8.2 GHz for receiver part, respectively. The clear eye diagram for transmitter part with 14.5 dB of the extinction ratio and 4.7 mW of output optical power and −26.3 dBm of receiver minimum sensitivity at a bit error rate of 10−10 are obtained under 2.488 Gbit/s operations.

Aberration analysis and efficiency improvement of a bidirectional optical subassembly

An approach to improve the coupling efficiency of bidirec- tional optical subassembly BOSA modules is proposed and experimen- tally demonstrated. We analyzed the wavefront aberration coefficients of a typical BOSA. It was found that the 45-deg wavelength filter induces coma and astigmatism, and then it further deteriorates the laser diode to fiber coupling. We measured the BOSA efficiencies based on a series of different filters. For a typical 0.5-mm filter, 25% coupling efficiency im- provement was achieved by optimizing the filter parameters. © 2009 Soci-

Optical-Beam-Induced-Current Analysis of Wear-Out Degradation in High-Reliability Fabry–Perot Laser Diodes for Access Networks

Reliability of a Fabry–Perot laser diode (FP-LD) that was developed for use in the bi-directional optical subassembly of access networks was investigated. Stable operation, which was closely related to the wear-out degradation, was confirmed from the results of an accelerated aging test at 85 °C, and a lifetime of over 2×105 h was estimated. To examine the behavior of the wear-out degradation in the FP-LD, we employed an optical-beam-induced-current (OBIC) analysis. From the results of the OBIC analysis, we found that large degradation occurs in the SCH layer rather than in the active layer in the early stage of the FP-LD's life.

High-Performance and Low-Cost 10-Gb/s Bidirectional Optical Subassembly Modules

High-performance and low-cost 10-Gb/s bidirectional optical subassembly (BOSA) modules that are obtained by adopting low-cost transistor outline (TO)-Can materials and processes are proposed and demonstrated. The BOSA module consists of an uncooled 1.3-mum distributed-feedback laser diode and a 1.5-mum p-i-n/transimpedance amplifier receiver (Rx), which integrate a 45deg tilted thin-film wavelength-division multiplexing filter to transmit a 1.3-mum light into the fiber and reflect a 1.55-mum light into the Rx. The matching resistor and low parasitic inductance packages are applied with the TO-Can laser diode to enable 10-Gb/s operation. A modulation bandwidth of 11.86 GHz and an OC-192 eye diagram of a 19% mask margin are obtained from the transmitter side. After a 10-km single-mode fiber (SMF) transmission, the mask margin for the OC-192 eye diagram decreases to 11%. For the Rx, an OC-192 eye diagram of a 31% mask margin is obtained under back-to-back connections. The mask margin is maintained at 29% after a 10-km SMF transmission. The measured crosstalk penalty is 0.9 d 15 at the Rx side. These results indicate that the BOSA module is capable of a 10-Gb/s bidirectional transmission. This unique high-performance 10-Gb/s BOSA module not only demonstrates the feasibility of a 10-Gb/s bidirectional transmission on an SMF for fiber-to-the-home applications but also shows the low-cost possibility to ensure the success of next-generation 10-Gb/s access networks.

A Novel Low-Cost Fiber In-Line-Type Bidirectional Optical Subassembly

A novel low-cost fiber in-line-type bidirectional optical subassembly using a tilted fiber Bragg grating has been developed for fiber-to-the-home applications. We successfully realized a low-cost subassembly by reducing the number of components and simplifying the packaging process. The extinction ratio of 14.8 dB, receiver minimum sensitivity of -26.5 dBm at a bit-error rate of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-12</sup> and frequency response of 2.7 GHz were experimentally obtained. The electrical crosstalk between transmitter and receiver part was less than -86 dB up to 2.5 GHz.

Bidirectional optical subassembly with prealigned silicon microlens and laser diode

We have succeeded in developing a low-cost bidirectional optical subassembly chip using a silicon microlens for fiber-to-the-home application. The main optical elements of the bidirectional function were automatically aligned and integrated on a silicon optical bench. The cost of subassembly was markedly lowered both by reducing the part number and simplifying the assembly process. The prototype bidirectional optical component was successfully fabricated on the basis of the proposed chip. A receiver minimum sensitivity of -28.5 dBm was experimentally demonstrated even at 75 degC