Jian Chen | University of Cambridge (original) (raw)

Papers by Jian Chen

Optical interconnects have attracted significant research interest for use in short-reach board-l... more Optical interconnects have attracted significant research interest for use in short-reach board-level optical communication links in supercomputers and data centers. Multimode polymer waveguides in particular constitute an attractive technology for on-board optical interconnects, as they provide high bandwidth, offer relaxed alignment tolerances, and can be cost-effectively integrated onto standard printed circuit boards (PCBs). However, the continuing improvements in bandwidth performance of optical sources make it important to investigate approaches to develop high-bandwidth polymer waveguides. In this paper, we present dispersion studies on a graded-index (GI) waveguide in siloxane materials designed to deliver high bandwidth over a range of launch conditions. Bandwidth-length products of >70 and ∼65 GHz×m are observed using a 50/125 μm multimode fibre (MMF) launch for input offsets of ±10 μm without and with the use of a mode mixer (MM), respectively; and enhanced values of >100 GHz×m are found under a 10× microscope objective launch for input offsets of ∼18 × 20 μm 2. The large range of offsets is within the –1 dB alignment tolerances. A theoretical model is developed using the measured refractive index profile of the waveguide, and general agreement is found with experimental bandwidth measurements. The reported results clearly demonstrate the potential of this technology for use in high-speed board-level optical links, and indicate that data transmission of 100 Gb/s over a multimode polymer waveguide is feasible with appropriate refractive index engineering.

Optical interconnects have attracted considerable attention for use in short-reach communication ... more Optical interconnects have attracted considerable attention for use in short-reach communication links within high-performance electronic systems, such as data centers, supercomputers, and data storage systems. Multimode polymer waveguides, in particular, constitute an attractive technology for use in board-level interconnects as they can be cost-effectively integrated onto standard PCBs and allow system assembly with relaxed alignment tolerances. However, their highly multimoded nature raises important concerns about their bandwidth limitations and their potential to support very high on-board data rates. In this paper, we report record error-free (BER < 10 −12) 40 Gb/s data transmission over a 1-m-long multimode polymer spiral waveguide and present thorough studies on the waveguide bandwidth performance. The frequency response of the waveguide is investigated under a wide range of launch conditions and in the presence of input spatial offsets, which are expected to be highly-likely in real-world systems. A robust bandwidth performance is observed with a bandwidth-length product of at least 35 GHz×m for all launch conditions studied. The reported results clearly demonstrate the potential of this technology for use in board-level interconnects, and indicate that data rates of at least 40 Gb/s are feasible over waveguide lengths of 1 m.

Multimode polymer waveguides constitute a promising technology for use in board-level optical int... more Multimode polymer waveguides constitute a promising technology for use in board-level optical interconnects. However, the continuous improvements in high-speed performance of VCSELs raise important questions about their ability to support such high data rates due to their inherent highly multimoded nature. Thorough experimental studies on the band-width of a 1.4-m-long multimode spiral waveguide are presented in this letter, indicating a bandwidth-length product of at least 35 GHz×m even in the case of an overfilled launch. No significant transmission impairments are observed for spatial input offsets, while error-free (BER < 10 −12) data transmission over the 1.4-m-long spiral waveguide is demonstrated at 25 Gb/s.

Multimode polymer waveguides are being increasingly considered for use in short-reach board-level... more Multimode polymer waveguides are being increasingly considered for use in short-reach board-level optical interconnects as they exhibit favourable optical properties and allow direct integration onto standard PCBs with conventional methods of the electronics industry. Siloxane-based multimode waveguides have been demonstrated with excellent optical transmission performance, while a wide range of passive waveguide components that offer routing flexibility and enable the implementation of complex on-board interconnection architectures has been reported. In recent work, we have demonstrated that these polymer waveguides can exhibit very high bandwidth-length products in excess of 30 GHz×m despite their highly-multimoded nature, while it has been shown that even larger values of > 60 GHz×m can be achieved by adjusting their refractive index profile. Furthermore, the combination of refractive index engineering and launch conditioning schemes can ensure high bandwidth (> 100 GHz×m) and high coupling efficiency (< 1 dB) with standard multimode fibre inputs with relatively large alignment tolerances (~17×15 µm 2). In the work presented here, we investigate the effects of refractive index engineering on the performance of passive waveguide components (crossings, bends) and provide suitable design rules for their on-board use. It is shown that, depending on the interconnection layout and link requirements, appropriate choice of refractive index profile can provide enhanced component performance, ensuring low loss interconnection and adequate link bandwidth. The results highlight the strong potential of this versatile optical technology for the formation of high-performance board-level optical interconnects with high routing flexibility.

A micromachined 300-GHz slotted waveguide antenna is demonstrated using a simple fabrication tech... more A micromachined 300-GHz slotted waveguide antenna is demonstrated using a simple fabrication technique based on metal-coated SU-8 thick resist. The antenna is designed to be built from a four-layer structure of equal layer thickness. It is fully characterized, and the measured radiation patterns show excellent agreement with the simulation. An H-plane matched right-angle bend is integrated in the antenna in order to achieve reliable and accurate connection with standard waveguide flange. The micromachined antenna is directional and low-profile and may find applications in low-cost sensors and radars.

Dispersion studies are conducted on 1m long multimode polymer spiral waveguides with different re... more Dispersion studies are conducted on 1m long multimode polymer spiral waveguides with different refractive index profiles. Bandwidth-length products >40GHz×m are obtained from such waveguides under a 50/125 μm MMF, indicating the potential of this technology.

Dispersion studies demonstrate that waveguide layout can be used to enhance the bandwidth perform... more Dispersion studies demonstrate that waveguide layout can be used to enhance the bandwidth performance of multimode polymer waveguides for use in board-level optical interconnects, providing >40 GHz×m without the need for any launch conditioning.

We report enhanced graded-index multimode polymer waveguides with >70GHz×m for MMF launch and >20... more We report enhanced graded-index multimode polymer waveguides with >70GHz×m for MMF launch and >200GHz×m for restricted launch, indicating the capability of on-board waveguide transmission of >100 Gb/s. Simulations using the measured refractive index profile agree well with the experiments.

Low-loss and high-bandwidth (>47 GHz×m) multimode polymer waveguide crossings (<0.02 dB/crossing)... more Low-loss and high-bandwidth (>47 GHz×m) multimode polymer waveguide crossings (<0.02 dB/crossing) and bends (<1dB) are demonstrated. The performance of passive optical backplanes comprising such components is also optimised using refractive-index engineering and launch conditioning.

We report enhanced bandwidth performance of >100 GHz×m over an offset range of ±10 μm in multimod... more We report enhanced bandwidth performance of >100 GHz×m over an offset range of ±10 μm in multimode polymer waveguides under restricted launch, demonstrating the capability to support on-board data rates of >100 Gb/s.

Advanced modulation formats can enable >40 Gb/s data rates in waveguide-based optical interconnec... more Advanced modulation formats can enable >40 Gb/s data rates in waveguide-based optical interconnects without the need for high-specification optoelectronic components. Record 56Gb/s PAM-4 data transmission is demonstrated over a 1 m-long multimode polymer waveguide.

We report record error-free data transmission of 40Gb/s over a 1m-long multimode polymer spiral w... more We report record error-free data transmission of 40Gb/s over a 1m-long multimode polymer spiral waveguide. The waveguide imposes no significant transmission impairments in the link despite its highly-multimoded nature and long length, demonstrating its potential in high-speed board-level optical interconnections.

Bandwidth measurements are conducted on a 1.4 m long spiral polymer multimode waveguide for a SMF... more Bandwidth measurements are conducted on a 1.4 m long spiral polymer multimode waveguide for a SMF and 50/125 µm MMF launch and for different input offsets. The waveguide exhibits a bandwidth of at least 30 GHz for all input types, yielding a bandwidth-length product of at least 42 GHz×m, while no impact is observed on the waveguide performance due to the different spatial input offsets. The results indicate that data transmission at data rates even higher than 25 Gb/s can be achieved over such structures, thereby demonstrating the potential of multimode polymer waveguide technologies in short-reach board-level datacommunication links.

A small-size CPW-feed multi-band planar monopole antenna is presented. A Swallow-Shaped-Patch (SS... more A small-size CPW-feed multi-band planar monopole antenna is presented. A Swallow-Shaped-Patch (SSP) that covers the Ultra-Wideband (UWB) frequency range is used in the proposed design. To create a multi-band antenna, several narrow pentagon slots, acting as resonance paths, can be integrated with the SSP antenna. Triple-band antennas are simulated and good results are obtained, while showing a very sharp band-rejection performance at 3.92 GHz, 5.34 GHz and 5.88 GHz, respectively. The antennas have omnidirectional and stable radiation patterns across all the relevant bands. Moreover, a prototype of the triple-band antenna is fabricated and measurement results are compared with simulation results.

Drafts by Jian Chen

The goal of this report is to tackle the “interconnection bottleneck” for board-level communicati... more The goal of this report is to tackle the “interconnection bottleneck” for board-level communications by investigating the high-speed performance of the polymer waveguide and multilevel modulation schemes so as to maximum the data transmission rate.

There are two main parts in this report: one is the high-performance studies on the polymer waveguide; the other one is the investigation on advanced modulation schemes. Although the dynamic characteristics of the polymer waveguide have been investigated intensively by Dr. Nikos Bamiedakis in the CPS, the performance of the spiral polymer waveguide is still not fully understood. So the first few chapters of this report are seeking to answer some of the questions such as how much bandwidth the spiral waveguide can support. The importance of this work is to determine if the current waveguide can support high data rate such as 25 Gb/s and beyond (e.g. 100 Gb/s). In addition, very little work has been done on the polymer waveguide using advanced modulations for high speed data transmission. Therefore, the last part of this report presents some studies on advanced modulation schemes based on the polymer waveguide system. Previously, 10 Gb/s data transmission based on the polymer waveguide has been demonstrated by Dr. Nikos and many other research groups. The purpose of this report is to investigate the approaches of increasing the data rate up to 25 Gb/s and beyond using advanced modulation formats.

Optical interconnects have attracted significant research interest for use in short-reach board-l... more Optical interconnects have attracted significant research interest for use in short-reach board-level optical communication links in supercomputers and data centers. Multimode polymer waveguides in particular constitute an attractive technology for on-board optical interconnects, as they provide high bandwidth, offer relaxed alignment tolerances, and can be cost-effectively integrated onto standard printed circuit boards (PCBs). However, the continuing improvements in bandwidth performance of optical sources make it important to investigate approaches to develop high-bandwidth polymer waveguides. In this paper, we present dispersion studies on a graded-index (GI) waveguide in siloxane materials designed to deliver high bandwidth over a range of launch conditions. Bandwidth-length products of >70 and ∼65 GHz×m are observed using a 50/125 μm multimode fibre (MMF) launch for input offsets of ±10 μm without and with the use of a mode mixer (MM), respectively; and enhanced values of >100 GHz×m are found under a 10× microscope objective launch for input offsets of ∼18 × 20 μm 2. The large range of offsets is within the –1 dB alignment tolerances. A theoretical model is developed using the measured refractive index profile of the waveguide, and general agreement is found with experimental bandwidth measurements. The reported results clearly demonstrate the potential of this technology for use in high-speed board-level optical links, and indicate that data transmission of 100 Gb/s over a multimode polymer waveguide is feasible with appropriate refractive index engineering.

Optical interconnects have attracted considerable attention for use in short-reach communication ... more Optical interconnects have attracted considerable attention for use in short-reach communication links within high-performance electronic systems, such as data centers, supercomputers, and data storage systems. Multimode polymer waveguides, in particular, constitute an attractive technology for use in board-level interconnects as they can be cost-effectively integrated onto standard PCBs and allow system assembly with relaxed alignment tolerances. However, their highly multimoded nature raises important concerns about their bandwidth limitations and their potential to support very high on-board data rates. In this paper, we report record error-free (BER < 10 −12) 40 Gb/s data transmission over a 1-m-long multimode polymer spiral waveguide and present thorough studies on the waveguide bandwidth performance. The frequency response of the waveguide is investigated under a wide range of launch conditions and in the presence of input spatial offsets, which are expected to be highly-likely in real-world systems. A robust bandwidth performance is observed with a bandwidth-length product of at least 35 GHz×m for all launch conditions studied. The reported results clearly demonstrate the potential of this technology for use in board-level interconnects, and indicate that data rates of at least 40 Gb/s are feasible over waveguide lengths of 1 m.

Multimode polymer waveguides constitute a promising technology for use in board-level optical int... more Multimode polymer waveguides constitute a promising technology for use in board-level optical interconnects. However, the continuous improvements in high-speed performance of VCSELs raise important questions about their ability to support such high data rates due to their inherent highly multimoded nature. Thorough experimental studies on the band-width of a 1.4-m-long multimode spiral waveguide are presented in this letter, indicating a bandwidth-length product of at least 35 GHz×m even in the case of an overfilled launch. No significant transmission impairments are observed for spatial input offsets, while error-free (BER < 10 −12) data transmission over the 1.4-m-long spiral waveguide is demonstrated at 25 Gb/s.

Multimode polymer waveguides are being increasingly considered for use in short-reach board-level... more Multimode polymer waveguides are being increasingly considered for use in short-reach board-level optical interconnects as they exhibit favourable optical properties and allow direct integration onto standard PCBs with conventional methods of the electronics industry. Siloxane-based multimode waveguides have been demonstrated with excellent optical transmission performance, while a wide range of passive waveguide components that offer routing flexibility and enable the implementation of complex on-board interconnection architectures has been reported. In recent work, we have demonstrated that these polymer waveguides can exhibit very high bandwidth-length products in excess of 30 GHz×m despite their highly-multimoded nature, while it has been shown that even larger values of > 60 GHz×m can be achieved by adjusting their refractive index profile. Furthermore, the combination of refractive index engineering and launch conditioning schemes can ensure high bandwidth (> 100 GHz×m) and high coupling efficiency (< 1 dB) with standard multimode fibre inputs with relatively large alignment tolerances (~17×15 µm 2). In the work presented here, we investigate the effects of refractive index engineering on the performance of passive waveguide components (crossings, bends) and provide suitable design rules for their on-board use. It is shown that, depending on the interconnection layout and link requirements, appropriate choice of refractive index profile can provide enhanced component performance, ensuring low loss interconnection and adequate link bandwidth. The results highlight the strong potential of this versatile optical technology for the formation of high-performance board-level optical interconnects with high routing flexibility.

A micromachined 300-GHz slotted waveguide antenna is demonstrated using a simple fabrication tech... more A micromachined 300-GHz slotted waveguide antenna is demonstrated using a simple fabrication technique based on metal-coated SU-8 thick resist. The antenna is designed to be built from a four-layer structure of equal layer thickness. It is fully characterized, and the measured radiation patterns show excellent agreement with the simulation. An H-plane matched right-angle bend is integrated in the antenna in order to achieve reliable and accurate connection with standard waveguide flange. The micromachined antenna is directional and low-profile and may find applications in low-cost sensors and radars.

Dispersion studies are conducted on 1m long multimode polymer spiral waveguides with different re... more Dispersion studies are conducted on 1m long multimode polymer spiral waveguides with different refractive index profiles. Bandwidth-length products >40GHz×m are obtained from such waveguides under a 50/125 μm MMF, indicating the potential of this technology.

Dispersion studies demonstrate that waveguide layout can be used to enhance the bandwidth perform... more Dispersion studies demonstrate that waveguide layout can be used to enhance the bandwidth performance of multimode polymer waveguides for use in board-level optical interconnects, providing >40 GHz×m without the need for any launch conditioning.

We report enhanced graded-index multimode polymer waveguides with >70GHz×m for MMF launch and >20... more We report enhanced graded-index multimode polymer waveguides with >70GHz×m for MMF launch and >200GHz×m for restricted launch, indicating the capability of on-board waveguide transmission of >100 Gb/s. Simulations using the measured refractive index profile agree well with the experiments.

Low-loss and high-bandwidth (>47 GHz×m) multimode polymer waveguide crossings (<0.02 dB/crossing)... more Low-loss and high-bandwidth (>47 GHz×m) multimode polymer waveguide crossings (<0.02 dB/crossing) and bends (<1dB) are demonstrated. The performance of passive optical backplanes comprising such components is also optimised using refractive-index engineering and launch conditioning.

We report enhanced bandwidth performance of >100 GHz×m over an offset range of ±10 μm in multimod... more We report enhanced bandwidth performance of >100 GHz×m over an offset range of ±10 μm in multimode polymer waveguides under restricted launch, demonstrating the capability to support on-board data rates of >100 Gb/s.

Advanced modulation formats can enable >40 Gb/s data rates in waveguide-based optical interconnec... more Advanced modulation formats can enable >40 Gb/s data rates in waveguide-based optical interconnects without the need for high-specification optoelectronic components. Record 56Gb/s PAM-4 data transmission is demonstrated over a 1 m-long multimode polymer waveguide.

We report record error-free data transmission of 40Gb/s over a 1m-long multimode polymer spiral w... more We report record error-free data transmission of 40Gb/s over a 1m-long multimode polymer spiral waveguide. The waveguide imposes no significant transmission impairments in the link despite its highly-multimoded nature and long length, demonstrating its potential in high-speed board-level optical interconnections.

Bandwidth measurements are conducted on a 1.4 m long spiral polymer multimode waveguide for a SMF... more Bandwidth measurements are conducted on a 1.4 m long spiral polymer multimode waveguide for a SMF and 50/125 µm MMF launch and for different input offsets. The waveguide exhibits a bandwidth of at least 30 GHz for all input types, yielding a bandwidth-length product of at least 42 GHz×m, while no impact is observed on the waveguide performance due to the different spatial input offsets. The results indicate that data transmission at data rates even higher than 25 Gb/s can be achieved over such structures, thereby demonstrating the potential of multimode polymer waveguide technologies in short-reach board-level datacommunication links.

A small-size CPW-feed multi-band planar monopole antenna is presented. A Swallow-Shaped-Patch (SS... more A small-size CPW-feed multi-band planar monopole antenna is presented. A Swallow-Shaped-Patch (SSP) that covers the Ultra-Wideband (UWB) frequency range is used in the proposed design. To create a multi-band antenna, several narrow pentagon slots, acting as resonance paths, can be integrated with the SSP antenna. Triple-band antennas are simulated and good results are obtained, while showing a very sharp band-rejection performance at 3.92 GHz, 5.34 GHz and 5.88 GHz, respectively. The antennas have omnidirectional and stable radiation patterns across all the relevant bands. Moreover, a prototype of the triple-band antenna is fabricated and measurement results are compared with simulation results.

The goal of this report is to tackle the “interconnection bottleneck” for board-level communicati... more The goal of this report is to tackle the “interconnection bottleneck” for board-level communications by investigating the high-speed performance of the polymer waveguide and multilevel modulation schemes so as to maximum the data transmission rate.

There are two main parts in this report: one is the high-performance studies on the polymer waveguide; the other one is the investigation on advanced modulation schemes. Although the dynamic characteristics of the polymer waveguide have been investigated intensively by Dr. Nikos Bamiedakis in the CPS, the performance of the spiral polymer waveguide is still not fully understood. So the first few chapters of this report are seeking to answer some of the questions such as how much bandwidth the spiral waveguide can support. The importance of this work is to determine if the current waveguide can support high data rate such as 25 Gb/s and beyond (e.g. 100 Gb/s). In addition, very little work has been done on the polymer waveguide using advanced modulations for high speed data transmission. Therefore, the last part of this report presents some studies on advanced modulation schemes based on the polymer waveguide system. Previously, 10 Gb/s data transmission based on the polymer waveguide has been demonstrated by Dr. Nikos and many other research groups. The purpose of this report is to investigate the approaches of increasing the data rate up to 25 Gb/s and beyond using advanced modulation formats.