Johan Bauwelinck

Development of GPON upstream physical-media-dependent prototypes

This paper presents three new gigabit-capable passive optical network (GPON) physical-media-dependent (PMD) prototypes: a burst-mode optical transmitter, an avalanche photodiode/transimpedance amplifier (APD-TIA), and a burst-mode optical receiver. With these, point-to-multipoint (P2MP) upstream transmission can be realized in a high-performance GPON at 1.25 Gb/s. Performance measurements on the new burst-mode upstream PMD modules comply with GPON uplink simulations. The laser transmitter can quickly set and stabilize the launched optical power level over a wide temperature range with better than 1-dB accuracy. A burst-mode receiver sensitivity of -32.8 dBm (BER=10/sup -10/) is measured, combined with a dynamic range of 23 dB at a fixed APD avalanche gain of 6. Full compliance is achieved with the recently approved ITU-T Recommendation G.984.2 supporting an innovative overall power-leveling mechanism.

Sensitivity penalty calculation for burst-mode receivers using avalanche photodiodes

This paper presents the sensitivity penalty for burst-mode receivers using avalanche photodiodes. The analysis takes into account detailed avalanche photodiode statistics, additive Gaussian noise, intersymbol interference and dc offsets in the receiver channel. The penalty has been calculated via comparison of bit-error rates (BERs), obtained using numerical integration, both in continuous- and burst-mode operation. Sensitivity penalties for burst-mode operation as a function of the mean avalanche gain are presented. The Gaussian approximation systematically underestimates the burst-mode penalty. It is shown that the penalty depends upon both the type of avalanche photodiode (APD) and the required BER. Optimum avalanche gains maximizing the sensitivity of the receiver are given. The influence of dc-offsets upon the sensitivity is studied. Furthermore, it is shown that the impulse response of the filters used to extract the decision threshold profoundly impacts the receiver performance. Finally, some important guidelines for the design of high sensitivity and wide dynamic range burst-mode receivers are given.

Nonintrusive Fiber Monitoring of TDM Optical Networks

This paper introduces a new embedded nonintrusive fiber-monitoring technique for time-division-multiplexing optical networks. It allows an optical transmitter to characterize the fiber plant from reflections caused by data bursts transmitted across the network instead of dedicated test signals. The probing is performed with minimal burden on data traffic so that many measurements can be averaged to improve accuracy. The method is very suitable for embedded optical time-domain reflectometers (OTDR), which reuse a network nodes optical data transmitter for OTDR excitations and embed a reflectometer inside the fiber endpoint. This paper models the OTDR with Laplace transforms, an approach previously unpursued, after which it is explained how reflections from multiple data bursts with arbitrary width can be converted into one normalized format. This new class of OTDR excites the fiber with a negative step of light instead of the conventional short pulse. The signal-to-noise ratio (SNR) for backscatter and Fresnel reflections caused by the negative step and pulse are compared theoretically. It is shown that negative-step OTDR breaks the tradeoff between excitation pulsewidth and distance resolution, has a natural separation between fiber backscatter and Fresnel reflectors, and improves the SNR of nonreflective events

GN-Model Validation Over Seven Fiber Types in Uncompensated PM-16QAM Nyquist-WDM Links

We report on a set of transmission experiments over seven different uncompensated fiber links carrying a 22-channel Nyquist-WDM signal comb based on polarization-multiplexed 16-quadrature amplitude modulation at RS=15.625 GBd(RB=125 Gb/s). The channel spacing was Δf=16 GHz. The experimental transmission performance was compared with analytical GN-model predictions showing a good agreement for all seven considered fiber types. Moreover, we used the experimental results for the validation of a fiber figure of merit based on the maximum reach, showing its effectiveness for approximate fiber performance prediction. Within the experimental tests, a maximum transmission distance of 3810 km at a bit error-rate of 1.5×10-2 was achieved using a pure-silica-core fiber with 150 μm2 effective area, at a net spectral-efficiency-distance product of 24700 (b·km)/(s· Hz), in a good agreement with the GN-model forecast.

A Novel Technique for Low-Cost Embedded Non-intrusive Fiber Monitoring of P2MP Optical Access Networks

A low cost embedded OTDR method is presented for monitoring the fiber plant of TDM optical networks without extra optical components nor performance penalty. It localizes abrupt changes in link attenuation without disturbing network operation.

An overview of passive optical networks

This paper gives an overview of past and recent developments of Passive Optical Networks (PONs). Such networks currently receive a lot of intention as a means to relieve the so-called last-mile bottleneck in todays broadband networks using optical fiber technology. Several important multiplexing techniques are highlighted, with an emphasis on Time Division Multiplexing (TDM). An overview of current standards is given, together with emerging standards for advanced broadband PON networks.

A 10Gb/s burst-mode TIA with on-chip reset/lock CM signaling detection and limiting amplifier with a 75ns settling time

Emerging symmetric 10Gb/s passive optical network (PON) systems aim at high network transmission efficiency by reducing the RX settling time that is needed for RX amplitude recovery in burst-mode (BM). A conventional AC-coupled BM- RX has an inherent tradeoff between short settling time and decision threshold droop, which makes an RX settling time shorter than 400ns hard to achieve. Some techniques have been developed to overcome this limitation, demonstrating a settling time of 150 to 200ns. Our previous work uses feed-forward automatic offset compensation (AOC) to achieve a response time as short as 25.6ns. However, a feed-forward scheme using peak detectors is intrinsically less accurate and results in relatively high power consumption. In this paper, we present a DC-coupled 10Gb/s BM-TIA and burst-mode limiting amplifier (BM- LA) chipset that uses a feedback type AOC circuit with switchable loop BW. This new technique is capable of removing input DC offset in less than 75ns, and offers continuous decision threshold tracking during payload, to cope with the maximum length of CID. The differential TIA output port senses a CM reset signal provided by the succeeding BM-LA, and activates an on-chip reset and lock function. This BM-LA also integrates auto reset/activity generation circuits providing the AOC BW switching signal, so that this time-critical signal is not required from the PON system.

Experiments on a 10 Gb/s fast-settling high-sensitivity burst-mode receiver with on-chip auto-reset for 10G-GPONs [Invited]

This paper presents a 10 Gb/s avalanche-photodiode-based DC-coupled reshaping and reamplifying (2R) burst-mode receiver with on-chip auto-reset generation and multiple data rate support, designed for 10G-GPONs. A short 2R settling time of 75 ns (150 ns for lower-rate operation), a high receiver sensitivity of -31.3 dBm, and a large loud/soft ratio of 25.3 dB are demonstrated at 2.5/5/10 Gb/s in burst-mode operation. Allowing multi-rate operation without external reset signals, it shows great potential for use in emerging symmetric 10G-GPON systems and allows for more flexible future optical access networks.

High Speed Direct Modulation of a Heterogeneously Integrated InP/SOI DFB Laser

An integrated laser source to a silicon photonics circuit is an important requirement for optical interconnects. We present direct modulation of a heterogeneously integrated distributed feedback laser on and coupled to a silicon waveguide. We demonstrate a 28 Gb/s pseudo-random bit sequence non-return-to-zero data transmission over 2 km non-zero dispersion shifted fiber with a 1-dB power penalty. Additionally, we show 40-Gb/s duobinary modulation generated using the bandwidth limitation of the laser for both back-to-back and fiber transmission configurations. Furthermore, we investigate the device performance for the pulse amplitude modulation (PAM-4) at 20 GBd for high-speed short-reach applications.

Flip-chip assembly of VCSELs to silicon grating couplers via laser fabricated SU8 prisms.

This article presents the flip-chip bonding of vertical-cavity surface-emitting lasers (VCSELs) to silicon grating couplers (GCs) via SU8 prisms. The SU8 prisms are defined on top of the GCs using non-uniform laser ablation process. The prisms enable perfectly vertical coupling from the bonded VCSELs to the GCs. The VCSELs are flip-chip bonded on top of the silicon GCs employing the laser-induced forward transfer (LIFT)-assisted thermocompression technique. An excess loss of < 1 dB at 1.55 µm measured from the bonded assemblies is reported in this paper. The results of high speed transmission experiments performed on the bonded assemblies with clear eye openings up to 20 Gb/s are also presented.