Kivilcim Yüksel

Optical layer monitoring in Passive Optical Networks (PONs): A review

Motivations, challenges and requirements of optical layer monitoring in PONs are discussed. An exhaustive review of monitoring systems is given considering both time-division multiplexed PON (TDM-PON) and wavelength-division multiplexed PON (WDM-PON) cases.

Analysis and suppression of nonlinear frequency modulation in an optical frequency-domain reflectometer

A new method for monitoring the nonlinearities perturbing the optical frequency sweep in high speed tunable laser sources is presented. The swept-frequency monitoring system comprises a Mach-Zehnder interferometer and simple signal processing steps. It has been implemented in a coherent optical frequency domain reflectometer which allowed to drastically reduce the effects of nonlinear sweep, resulting to a spatial resolution enhancement of 30 times.

Optical frequency domain reflectometry: A review

In this paper, we discuss the operation principles, challenges and application areas of optical frequency domain reflectometry technique. A review of OFDR systems is given considering both Incoherent-OFDR and Coherent-OFDR groups. Results obtained by different research groups are compared in terms of performance characteristics, and future perspectives. Recent progresses obtained within our laboratory are also presented.

Centralised Optical Monitoring of Tree-structured Passive Optical Networks using a Raman-assisted OTDR

Monitoring of tree-structured passive optical networks from a central office is difficult to achieve using a standard OTDR. Switchable reflective elements placed at the ONU can help to discriminate between the branches. In parallel, a Raman assisted OTDR is shown to increase the dynamic range of the reflectometry measurement, thus enabling to detect more faults in the network, and especially fibre breaks after the splitter.

A quasi-distributed temperature sensor interrogated by optical frequency-domain reflectometer

This paper presents the analysis of a quasi-distributed sensor based on the concatenation of identical low-reflective fiber Bragg gratings. We experimentally demonstrated a temperature sensor using ten cascaded gratings which are interrogated by an optical frequency domain reflectometer. Repeatability measurements highlighted a standard deviation on the measured temperature smaller than 1.5 °C. A complete demonstration of mathematical formulas which are used to obtain the temperature information is also provided.

Complete Analysis of Multireflection and Spectral-Shadowing Crosstalks in a Quasi-Distributed Fiber Sensor Interrogated by OFDR

We present the analysis of a quasi-distributed fiber sensor based on the concatenation of identical low-reflective fiber Bragg gratings (FBGs) taking into account both multireflection and spectral-shadowing crosstalks. This allows obtaining more realistic values of the design parameters such as the maximum number of sensing points, the reflectivity of the gratings, and the distance between the sensing points.

Signal Processing, Management and Monitoring in Transmission Networks

For transparent optical networks, it is important to support the demanded signal quality of physical paths from source to destination nodes, in response to a given call request. Due to the lack of regeneration in current optical networks, optical signal impairments accumulate along paths. With channel bit rates of 10 Gbit/s or higher, linear and non-linear fibre impairments become prominent factors affecting the signal quality. Thus, new techniques in both physical layer and network layer are necessary for mitigating impairments to accommodate high-speed traffic (Tomkos et~al. 2002).

Analysis of spectral-shadowing crosstalk in a quasi-distributed fibre sensor interrogated by optical frequency-domain reflectometer

We present the analysis of a quasi-distributed fibre sensor based on the concatenation of identical low-reflective fiber Bragg gratings (FBGs) taking into account the effect of spectral-shadowing crosstalk. This allows obtaining more realistic values of the design parameters such as the maximum number of sensing points, the reflectivity of the gratings, and the distance between the sensing points.

Original monitoring technique for passive optical networks combining fiber Bragg gratings and wavelength swept light source

An efficient monitoring method having a very short measurement time (a few seconds) is proposed. The equal-length branches can be effectively monitored, but also the information of temperature at any place in the network can be obtained. The feasibility of this technique is experimentally demonstrated.

Infrared radiation detector interrogated by Optical Frequency Domain Reflectometer (OFDR)

We experimentally demonstrated a fast infrared radiation sensor. The system is applicable in a quasi-distributed configuration to cover a large area using a single interrogation unit (OFDR) for early fire detection.