Receiver Optical Sub-assembly Research Articles

Silica-Based Hybrid-Integrated Receiver Optical Subassembly for 400 Gbps Ethernet

A silica-based hybrid-integrated receiver optical subassembly (ROSA) for 400 Gbps Ethernet (400GbE) is demonstrated, which consists of an 8-channel silica-based arrayed waveguide grating (AWG), two 4-channel InP-based surface-illuminated photodetector (PD) arrays, two 4-channel transimpedance amplifier (TIA) arrays, and a high-frequency flexible printed circuit (FPC). All lanes of the ROSA exhibit responsivities of over 0.539 A/W, 3-dB bandwidths of greater than 30.86 GHz, and receiver sensitivities of less than −11.7 dBm. The ROSA has achieved a transmission rate of 8 × 50 Gbps for data center interconnect.

Novel low-cost high-speed optic–electric laser diode pigtail module packaging technology

• At present, the research and development of high-speed laser modules for communication are designed with ceramic components globally. • In module packaging without the ceramic part, the misalignment caused by the deformation results in coupling efficiency loss. • A new type of high-speed laser diode pigtail module is designed to change the structure of a laser module and remove ceramic and process parts. • A laser diode pigtail module package achieves the best coupling efficiency. A high-speed laser diode pigtail for wide-band fiber-optic communications is a key component in optical fiber user loop systems, optical fiber data communication systems, and cable television systems. With the advent of a new type of optic–electric high-speed laser, wide-band communication has emerged. These three systems constitute future mainstreams of optical fiber communications. However, high-speed laser diode pigtails used in module components and process assembly account for extremely high production costs. The proposed pigtail module eliminates ceramic parts and facilitates mass production of the components. An optic fiber (including a jacket) was placed into a ferrule sleeve. The optic fiber did not undergo laser damage, and its stability in the reliability test was ensured by the plastic jacket. The optic fiber terminal surfaces grind the 7° angle to enhance the surface quality of the connector, thereby avoiding reflection and incurring a power loss of 4%. Moreover, achieving alignment in a conventional laser module package without a ceramic part and fiber ferrule is a considerable challenge, and apparently, there are still some issues that need to be resolved. In conventional optical fiber module package, laser welding technique provides a superior joint strength. However, in module packaging without the ceramic part, the misalignment caused by the deformation results in coupling efficiency loss. Therefore, a novel design of laser diode pigtail module packaging is necessary. A transmitter optical subassembly device, receiver optical subassembly device, and transceiver pigtail module can be manufactured in a unified process package. By applying the low-cost packaging technique, the cost and fabrication time of the module packaging were reduced, and the fabrication yield was increased.

5G-Compatible IF-Over-Fiber Transmission Using a Low-Cost SFP-Class Transceiver

With the rise of 5G and beyond, the ever-increasing data-rates demanded by mobile access are severely challenging the capacity of optical fronthaul networks. Despite its high reliability and ease of deployment, legacy digital radio-over-fiber (RoF) technologies face an upcoming bandwidth bottleneck in the short term. This has motivated a renewed interest in the development of analog RoF alternatives, owing to their high spectral efficiency. However, unlike its digital counterpart, analog RoF transmission requires a highly linear transceiver to guarantee signal fidelity. Typical solutions exploited in recent research works tend to adopt the use of bulky benchtop components, such as directly modulated lasers (DML) and photodiodes. Although this provides a convenient and quick path for proof-of-concept demonstrations, there is still a considerable gap between lab developments and commercial deployment. Most importantly, a key question arises: can analog-RoF transceivers meet the 5G requirements while being competitive in terms of cost and footprint? Following this challenge, in this work we exploit the use of a low-cost commercial off-the-shelf (COTS) small form-factor pluggable (SFP) transceiver, originally designed for digital transmission at 1 Gbps, which is properly adapted towards analog RoF transmission. Bypassing the digital electronics circuitry of the SFP, while keeping the original transmitter optical sub-assembly (TOSA) and receiver optical sub-assembly (ROSA), we demonstrate that high-performance 5G-compatible transmission can be performed by reusing the key built-in components of current low-cost SFP-class transceivers. Particularly, we demonstrate error vector magnitude (EVM) performances compatible with 5G 64QAM transmission both at 100MHz and 400MHz. Furthermore, employing a memory polynomial model for digital pre-distortion of the transmitted signal, we achieve 256QAM-compatible performance at 100MHz bandwidth, after 20 km fronthaul transmission.

LDLA14: a 14 Gbps optical transceiver ASIC in 55 nm for NICA multi purpose detector project

This paper presents the design and test results of a 14 Gbps optical transceiver ASIC (LDLA14) fabricated in a 55 nm CMOS technology for NICA Multi Purpose Detector (MPD) project. The LDLA14 is a single-channel bidirectional (1Tx + 1Rx) optical transceiver ASIC, including a Laser Driver (LD) module and a Limiting Amplifier (LA) module. It would drive the Vertical Cavity Surface Emitting Laser (VCSEL) of Transmitter Optical Sub-Assembly (TOSA) and receive signals from Photo Diode (PD) of Receiver Optical Sub-Assembly (ROSA), respectively. In the LDLA14, a novel structure of capacitive coupling pre-emphasis is proposed in the output driver of LD to obtain peaking effect without sacrifice the modulation current swing. A shared inductor technology and a Continuous Time Linear Equalizer (CTLE) pre-emphasis structure are added in the output buffer of LA to improve the quality of the output eye diagram. The dimension of LDLA14 is 1.5 mm × 1.3 mm, and the power consumption is 178 mW. The Peak-to-Peak Jitter (PPJ) and Root-Mean-Square Jitter (RMSJ) of the 14 Gbps optical eye diagram of LD in the Tx direction are 22.5 ps and 3.5 ps, respectively. The PPJ and RMSJ of the 14 Gbps electrical eye diagram of LA in the Rx direction are 23.1 ps and 4.7 ps, respectively. The BER tests have been conducted in Tx, Rx directions and the Tx-Rx loop condition, and the BER less than 10−12 is achieved in all tests.

A 10-Gb/s Driver/Receiver ASIC and Optical Modules for Particle Physics Experiments

We present the design and test results of a Drivers and Limiting AmplifierS ASIC operating at 10 Gb/s (DLAS10) and three miniature optical transmitter/ receiver/transceiver modules (MTx+, MRx+, and MTRx+) based on DLAS10. DLAS10 can drive two transmitter optical subassemblies (TOSAs) of vertical cavity surface emitting lasers (VCSELs), receive the signals from two receiver optical subassemblies (ROSAs) that have no embedded limiting amplifiers (LAs), or drive a VCSEL TOSA and receive the signal from a ROSA, respectively. Each channel of DLAS10 consists of an input continuous time linear equalizer (CTLE), a four-stage LA, and an output driver. The LA amplifies the signals of variable levels to a saturation amplitude of 800 mV (peak-peak). The output driver drives VCSELs or impedance-controlled traces. DLAS10 is fabricated in a 65-nm CMOS technology. The die is 1 mm ×1 mm. DLAS10 is packaged in a 4 mm ×4 mm 24-pin quad-flat no-leads (QFNs) package. DLAS10 has been tested in MTx+, MRx+, and MTRx+ modules. Both measured optical and electrical eye diagrams pass the 10-Gb/s eye mask test. The input electrical sensitivity is 40 mVp-p, while the input optical sensitivity is -12 dBm. The total jitter of MRx+ is 29 ps (P-P) with a random jitter of 1.6 ps (rms) and a deterministic jitter of 9.9 ps. Each MTx+/MRx+ module consumes 82.6 and 174.4 mW/ch, respectively.

Verification of hybrid-integrated 400-Gb/s (4 × 100 Gb/s) CWDM4 ROSA using a bandwidth-improved multilayer board.

We have successfully demonstrated a hybrid-integrated 400-Gb/s (4 × 100 Gb/s) CWDM4 PAM-4 receiver optical sub-assembly (ROSA) with a bandwidth-improved multilayer evaluation board. The proposed ROSA offers packaging simplification through passive optical alignment assembly of main components. In addition, we have proposed a structure to mitigate the bandwidth limitation issue caused by the typical edge connector mounting on the multilayer board, when needed bandwidth exceeds ∼20 GHz. With the bandwidth-improved multilayer board, the 3-dB bandwidth of the ROSA was observed to be >35.7 GHz and its receiver sensitivity was successfully measured to be <-10 dBm at FEC limit, bit error rate of 2.4e-4, for all channels.

A Compact Integrated Receiver Optical Sub-Assembly With High Sensitivity and Low Crosstalk for 100 Gb/s Ethernet Systems

A 25Gb/s guardring-free planar AlInAs avalanche photodiode (APD) and 100-Gb/s APD receiver optical sub-assembly (ROSA) employing a quasi-collimated beam for reducing the optical loss and optical demultiplexer (DEMUX) size are demonstrated for a 40-km optical link. The APD so fabricated achieves a very low dark current of 63 nA at a multiplication factor of 10, with a high gain-bandwidth product of 225 GHz due to the optimum multiplication layer and absorption layer. Additionally, the assembled APD ROSA exhibits a high receiver sensitivity of more than −23 dBm optical modulation amplitude (OMA) (BER = 5.0 × 10−5) at temperatures ranging from −5 to 80 °C for each lane. Investigating the transmission over fibers with dispersions of −119 and +40 ps/nm reveals that a sufficiently low penalty of less than 0.9 dB is obtained for all lanes. Furthermore, it is confirmed that the APD ROSA suffers little crosstalk penalty thanks to the isolation achieved by this design of optical DEMUX.

Eight-wavelength receiver optical subassembly based on silica hybrid integrated technology

A receiver optical subassembly (ROSA) based on hybrid integrated technology is designed and fabricated. It consists of an 8-channel arrayed waveguide grating (AWG) with 2% refractive index difference, two 4-channel positive intrinsic-negative photodetector arrays, and two 4-channel transimpedance amplifier arrays. A flat-top optical spectrum was observed because the output waveguides have a multimode structure, and the average 1-dB bandwidth of AWG channels is 2.8 nm. The insertion loss of all channels is between −1.8 and −2.9 dB, and the cross talk between adjacent channel is less than −20 dB. The ROSA shows a maximum responsivity of 0.4 A / W and 3-dB bandwidth of more than 22 GHz for four channels, which can meet the data transmission rate of 25 Gb / s. In the future, we will improve the fabrication process to achieve a transmission rate of 8 × 25 Gb / s.

Low-cost hybrid integrated 4 × 25 GBaud PAM-4 CWDM ROSA with a PLC-based arrayed waveguide grating de-multiplexer

We demonstrate a low-cost hybrid integrated and compact 100 GBaud four-lane coarse wavelength division multiplexing (CWDM) receiver optical sub-assembly (ROSA) based on an arrayed waveguide grating de-multiplexer in the O band. To achieve the horizontal light coupling between the planar light-wave circuit (PLC) based arrayed waveguide grating de-multiplexer and photodetector array, a 42° polished facet is applied for total reflection. A flexible printed circuit with high-frequency coplanar waveguides is used for a power supply of trans-impedance amplifier and signal transmission. The fabricated CWDM ROSA module, whose size is 18 mm×22 mm×6 mm, shows a 3 dB bandwidth of 21.2, 18.4, 19.6, and 19.3 GHz, respectively, in each lane. The overall symbol error rates are at a magnitude of 10−7 for 25 GBaud four-level pulse amplitude modulation (PAM-4) transmission with an average input optical power of 5 dBm.

A TOSA/ROSA-based optical transmitter (MTx+)/transceiver (MTRx+) for high-energy physics experiments

We present a dual-channel optical transmitter (MTx+)/transceiver (MTRx+) for the front-end readout electronics of high-energy physics experiments. MTx+ utilizes two Transmitter Optical Sub-Assemblies (TOSAs) and MTRx+ utilizes a TOSA and a Receiver Optical Sub-Assemblies (ROSA). Both MTx+ and MTRx+ receive multimode fibers with standard Lucent Connectors (LCs) as the optical interface and can be panel or board mounted to a motherboard with a standard Enhanced Small Form-factor Pluggable (SFP+) connector as the electrical interface. MTx+ and MTRx+ employ a dual-channel Vertical-Cavity Surface-Emitting Laser (VCSEL) driver ASIC called LOCld65, which brings the transmitting data rate up to 14 Gbps per channel. MTx+ and MTRx+ have been tested to survive 4.9 kGy(SiO2).

1.3-µm 4×25-Gb/s hybrid integrated TOSA and ROSA

The design and fabrication of a compact and low-cost 4×25-Gb/s transmitter optical sub-assembly (TOSA) and receiver optical sub-assembly (ROSA) using a hybrid integrated technique are reported. TOSA and ROSA are developed without thermoelectric cooler for coarse wavelength division multiplexing applications. Physical dimension of the packaged optical subassembly is limited to 11.5 mm×5.4 mm×5.4 mm. The design of TOSA and ROSA is employed using a silica-based arrayed waveguide grating chip to select the specific channel wavelength at O-band. In TOSA, the wavelength of four 1.3-µm discrete directly modulated laser chips is well controlled based on the reconstruction equivalent chirp technique. In the back-to-back transmission test, bit error rates for all lanes of cascade of the TOSA and ROSA are small. A clear opening eye diagram is obtained.

Ultra-compact four-lane hybrid-integrated ROSA based on three-dimensional microwave circuit design

An ultra-compact hybrid-integration receiver optical subassembly (ROSA) with four channels is demonstrated in our laboratory with the size of 23.3 mm × 6.0 mm × 6.5 mm. The ROSA is comprised of a planar lightwave circuit (PLC) arrayed waveguide grating (AWG) chip, a top-illuminated positive-intrinsic-negative photodetector array chip, and a three-dimensional microwave circuit that is specially designed for compact packaging. For each transmission lane, the −3 dB bandwidth of the ROSA is up to 20 GHz, and the maximum responsivity is up to 0.53 A/W. The proposed package structure can be used for smaller package sizes and would be an easy assembling solution for 100 GbE optical communication devices.

Power budget of 25-Gb/s digital orthogonal filter multiple access PONs with 10G-class optics

Abstract Power budget is a key factor that should be considered in intensity modulation and direct detection (IM/DD) passive optical networks (PONs). Based on the low-cost 10G-class electro-absorption modulated laser (EML) operating at C-band, we not only experimentally and theoretically investigate the interplay between the chromatic dispersion, the chirp of EML, and the self-phase modulation (SPM), but also explore the influences of the resolution and timing jitter of the analog to digital converter (ADC). Both theoretical and experimental results show that high power budget can be effectively achieved by making full use of the high launch power induced SPM effect and EML-induced frequency chirp. Based on the 10-G transmitter optical sub-assembly (TOSA) and receiver optical sub-assembly (ROSA), we successfully realize 25 Gb/s signal transmission at C-band over 25 km standard single mode fiber (SSMF) in IM/DD PON system. Even the worst performing bands can still achieve 25 dB power budget. The proposed scheme in this work has a potential application in future cost-effective optical access networks.

Low-cost and miniaturized 100-Gb/s (2 × 50 Gb/s) PAM-4 TO-packaged ROSA for data center networks.

We design and implement a cost-effective and compact 100-Gb/s (2 × 50 Gb/s) PAM-4 receiver optical sub-assembly (ROSA) by using a TO-can package instead of an expensive box-type package. It consists of an optical demultiplexer, two PIN-PDs and a 2-channel linear transimpedance amplifier. The components are passively aligned and assembled using alignment marks engraved on each part. With a real-time PAM-4 DSP chip, we measured the back-to-back receiver sensitivities of the 100-Gb/s ROSA based on TO-56 to be less than -13.2 dBm for both channels at a bit error rate of 2.4e-4. The crosstalk penalty due to the adjacent channel interference was observed around 0.1 dB.

4?×?20 GHz silica-based AWG hybrid integrated receiver optical sub-assemblies

Both the 4×20 GHz coarse wavelength division multiplexing and LAN-WDM receiver optical sub-assemblies (ROSAs) were developed. The ROSA package was hybrid integrated with a planar lightwave circuit arrayed waveguide grating (AWG) with 2% refractive index difference and a four-channel top-illuminated positive-intrinsic-negative photodetector (PD) array. The output waveguides of the AWG were designed in a multimode structure to provide flat-top optical spectra, and their end facet was angle-polished to form a total internal reflection interface to realize vertical coupling with a PD array. The maximum responsivity of ROSA was about 0.4 A/W, and its 3 dB bandwidth of frequency response was up to 20 GHz for each transmission lane. The hybrid integrated ROSA would be a cost-effective and easy-assembling solution for 100 GbE data center interconnections.

The 8×10 GHz Receiver Optical Subassembly Based on Silica Hybrid Integration Technology for Data Center Interconnection**Supported by the National High Technology Research and Development Program of China under Grant No 2015AA016902, the National Natural Science Foundation of China under Grant Nos 61435013 and 61405188, and the K. C. Wong Education Foundation.

An 8×10 GHz receiver optical sub-assembly (ROSA) consisting of an 8-channel arrayed waveguide grating (AWG) and an 8-channel PIN photodetector (PD) array is designed and fabricated based on silica hybrid integration technology. Multimode output waveguides in the silica AWG with 2% refractive index difference are used to obtain flat-top spectra. The output waveguide facet is polished to 45° bevel to change the light propagation direction into the mesa-type PIN PD, which simplifies the packaging process. The experimental results show that the single channel 1 dB bandwidth of AWG ranges from 2.12 nm to 3.06 nm, the ROSA responsivity ranges from 0.097 A/W to 0.158 A/W, and the 3 dB bandwidth is up to 11 GHz. It is promising to be applied in the eight-lane WDM transmission system in data center interconnection.

Dark Current Leakage in Optoelectronic Hermetic Packages

Abstract In this work, the root cause of the increase in dark current occurring over time at high temperature in hermetic packages, such as those used in optoelectronic devices, was investigated. It was observed that hermetic Receiver Optical Subassembly (ROSA) devices show continuously increasing dark current when stressed and monitored at 85°C over an extended period of time, reaching, in some cases, values greater than 500nA. However, this increase in leakage current was recoverable once the package seal is broken, and this behavior was found to be very repeatable. Photodetectors from two different suppliers were tested and found to have dark current which is dependent on the fabrication process, as the photodetector (PD) from supplier 1 (PD1) showed three times higher leakage than the photodetector from supplier 2 (PD2). The main difference between the two photodetectors is that the polyimide layer in PD1 in significantly greater than in PD2. It was also observed that 48 hour pre-seal baking at 120°C keeps the dark current constant at much lower levels, but does not stop it completely from rising over time.

SWDM PAM4 Transmission From 850 to 1066 nm Over NG-WBMMF Using 100G PAM4 IC Chipset With Real-Time DSP

The 53.125 Gbps transmission is experimentally investigated over a next-generation wideband multimode optical fiber (NG-WBMMF) using transmitter optical sub-assemblies (TOSAs) and wideband receiver optical sub-assemblies (ROSAs) developed for 25 Gbps short wavelength division multiplexing (SWDM) operation. A commercial 100 Gbps four-level pulse amplitude modulation integrated circuit (PAM4 IC) evaluation kit with real-time digital signal processing (DSP) is used. Dual wavelength transmission (2 λ × 53.125 Gbps) tests over 300 m of NG-WBMMF are carried out for the wavelength pairs 850, 880 nm and 910, 940 nm with a 4 × 1 optical MUX/DeMUX in the link. Measured pre-forward error correction (FEC) bit error ratio (BER) below the KP4 FEC threshold of 2.4 × 10–4 indicates the feasibility of 100/200 Gbps transmission over NG-WBMMF using a PAM4 chipset with real-time DSP. Single wavelength transmission (1 λ × 53.125 Gbps) using long wavelength TOSAs at 976 and 1066 nm is also studied. Pre-FEC BER below 2.4 × 10–4 is achieved over 300 m at 976 nm and 200 m at 1066 nm. Single wavelength tests from 850 to 940 nm had the same results as the 976 nm wavelength. Thus, this is the first experiment which shows the potential of 400 Gbps transmission with eight SWDM wavelength windows over a single NG-WBMMF using SWDM TOSAs, ROSAs, and commercial 100 Gbps PAM4 chipset.

Highly alignment tolerant and high-sensitivity 100Gb/s (4 × 25Gb/s) APD-ROSA with a thin-film filter-based de-multiplexer.

We investigate and demonstrate a 100-Gb/s (4x25-Gb/s) receiver optical sub-assembly (ROSA) based on avalanche photodiodes and a thin-film filter-based de-multiplexer. The overall alignment tolerances of the ROSA are relaxed to have larger than ± 25 μm by improving optical coupling structure. The receiver sensitivity of each lane is also measured to be less than -22.2 dBm, a record minimum to our knowledge, at the bit error ratio of 10-12 for 25.78-Gb/s NRZ signal.

Bidirectional optical subassembly-shaped 20 - Gbit / s compact single-mode four-channel wavelength-division multiplexing optical modules for optical multimedia interfaces

Low-cost single-mode four-channel optical transmitter and receiver modules using the wavelength-division multiplexing (WDM) method have been developed for long-reach fiber optic applications. The single-mode four-channel WDM optical transmitter and receiver modules consist of two dual-wavelength optical transmitter and receiver submodules, respectively. The integration of two channels in a glass-sealed transistor outline-can package is an effective way to reduce cost and size and to extend the number of channels. The clear eye diagrams with more than about 6 dB of the extinction ratio and the minimum receiver sensitivity of lower than −16 dBm at a bit error rate of 10−12 have been obtained for the transmitter and receiver modules, respectively, at 5 Gbps/channel. The 4K ultrahigh definition contents have been transmitted over a 1-km-long single-mode fiber using a pair of proposed four-channel transmitter optical subassembly and receiver optical subassembly.