Luis E. Y. Herrera

WDM-PON Monitoring With Tunable Photon Counting OTDR

We explore the performance of a tunable optical time domain reflectometer based on single photon detection for fault location and quantification in wavelength division multiplexing (WDM)-passive optical networks based on a 32-channel cyclic arrayed waveguide grating using the S- and C-bands for upstream (156 Mb/s) and downstream (2.5 Gb/s) transmission and the L-band for monitoring. Downstream Rayleigh and Raman scattering contributions to the dark count noise were evaluated and properly filtered out with a total WDM + filter rejection ratio of 90 dB. Upstream power was found to generate the greatest contribution to the noise floor and is the limiting factor to the upstream transmission data rate. In-service monitoring experiments with full upstream and downstream power show that the proposed scheme is able to achieve dynamic range levels of up to 32 dB with 5-m spatial resolution and no measurable penalty in data transmission.

Automatic Fault Detection in WDM-PON With Tunable Photon Counting OTDR

An automatic fiber-optical fault analysis system making use of a tunable photon counting optical time-domain reflectometry (OTDR) (ν-OTDR) is proposed and demonstrated in a passive optical network testbed. The employment of the ℓ trend filter as a signal processing tool enables the minimization of the intrinsic coherent random noise impact on the acquired data and also an automatic identification of fiber faults. A feedback loop between an FPGA-based acquisition unit and the filters selections yields highly accurate automatic results and minute monitoring periods with ITU-T grid DWDM tunability, spatial resolution of 6 m and a measured 32 dB dynamic range.

Investigation of bend loss in single mode fibers with ultra-high-resolution photon-counting optical time domain reflectometer

An intensity peak associated with fiber bending could be detected thanks to the use of an ultra-high-resolution photon-counting optical time domain reflectometer (OTDR) setup. The peak intensity is shown to be dependent on the curvature radius and angular distance of the bend. To account for such peaks, we propose a model based on modal mismatching and coupling inside the bend region and show that the model is highly consistent with the acquired data. Combining the information of the bend peak and bend loss, and taking advantage of the high dependence of the peak value with the local modal field parameter, the technique could be employed as an optical fiber local-parameter characterization method.

Ultra-high-resolution tunable PC-OTDR for PON monitoring in avionics

We present a setup for detecting and evaluating fiber curvatures using high-resolution Photon-Counting OTDR. Our setup is based on a Time-to-Digital Converter which can account for a resolution of up to 2,8 centimeters.

High resolution automatic fault detection in a fiber optic link via photon counting OTDR

We present an automatic method for detecting and evaluating fault events in a fibre link. Two Photon Counting OTDR setups are presented (3.5 cm, 12 dB and 2.25 m, 29 dB) allied to a signal processing technique for automatic results.

High-Dynamic and High-resolution Automatic Photon Counting OTDR for Optical Fiber Network Monitoring

In this work, the development of a hybrid structure for the monitoring of optical fibers, using two types of Photon Counting Optical Time Domain Reflectometers (ν-OTDR), is presented. While one ν-OTDR presents a 32 dB dynamic range with spatial resolution of 6 m and minute-range measurements, the other has a 14 dB dynamic range and a resolution of 3 cm with hour-range measurements. By employing a trend filter capable of detecting fiber faults in the ν-OTDR fiber profile and interchanging between either OTDR techniques in an automatic fashion, we were able to harness the qualities of both in the minimum amount of measurement time. Our experimental results performed with multiple optical fiber links attest the structure’s capability of automatically detecting faults in an optical fiber link with ultra-high-resolution and minute-range measurements. Furthermore, tunability of the hybrid structure enabling the monitoring of wavelength-division multiplexed optical networks has been demonstrated.

Linearized Electro-Optical Modulation for Analog Radio over Fiber

ABSTRACT Intermodulation distortion (IMD) in Analog Radio-over-Fiber (a-RoF) poses a severe limitation to achievable error-free transmission. In this work, an optical feed-forward linearization scheme is presented and compared to an electrical pre-distortion solution. Both techniques show identical performance for intermodulation compensation of neighboring frequencies. The former suits wideband multi-carrier transmission better because it does not present limited operational bandwidth. Proof-of-concept experiments for reducing intermodulation and distortions are offered. A 5-dB improvement in the Error Vector Magnitude (EVM) distortion floor level is achieved. Trade-off between compensating for second and third harmonics was verified. Results indicate the solution allows maximal exploitation in a-RoF capacity.

Single-tone multiple copper line monitoring in frequency-reusable fiber-extended copper line architectures

We propose a frequency-reusable architecture for fiber-extend copper lines with spectrally efficient multiple copper line monitoring. In-service simultaneous multi-copper and fiber monitoring is possible with the right choice of frequency bands, a result backed by the Error Vector Magnitude measurement of data channels in simultaneous coexistence with monitoring channels. The proposed monitoring method enables centralized single-ended line testing of hybrid fiber-copper architectures.

Experimental Demonstration of SCM-PON Monitoring with Baseband Embedded OTDR

ABSTRACT The combination of subcarrier multiplexing and passive optical networks can provide an efficient and cost-effective solution for fiber and wireless convergence in access networks. Moreover, to reduce operational expenditures, a reliable monitoring technique should provide in-service evaluation of the physical layer. Here, we perform the experimental demonstration of an SCM-PON system with baseband embedded optical time-domain reflectometer monitoring. Different modulation formats were tested to evaluate the penalty generated by the monitoring system. Based on the long-term evolution downlink test model (E-TM 3.1), our results show negligible power penalty while achieving a ~12-dB dynamic range with 10-m spatial resolution.

Time-polarization multiplexing for increased output power of semiconductor optical amplifiers in the pulsed regime

We present a setup capable of overcoming the saturation output power of semiconductor optical amplifiers operating in the pulsed regime. The concept is to couple different time delays to orthogonal polarization modes, amplify the pulses multiplexed in time, and use the polarization information to recombine them into a single high-power optical pulse. Making use of a single amplifier and two polarizing beam splitters, we were able to amplify pulses with as much as 1.9 dB above the saturation output power of the device. We also show that the method is scalable if any number of polarizing beam splitters is available, where each extra device contributes roughly 1.9 dB to the overall above-saturation amplification factor.