Postdoctoral Researcher in Vulnerability Assessment of a PON (Passive Optical Network) Telecom Access Network against Potential Eavesdropping by DAS (Distributed Acoustic Sensor) - 12-month Fixed-Term Contract

Who are we?

Télécom Paris, a school within IMT (Institut Mines-Télécom) and a founding member of Institut Polytechnique de Paris, is a top 5 French engineering school.

The Purpose of Télécom Paris is to train, imagine, and undertake to design digital models, technologies, and solutions for the service of a society and economy that respects people and their environment.

We are looking for our future postdoctoral researcher in vulnerability assessment of a PON (Passive Optical Network) telecom access network against potential eavesdropping by DAS (Distributed Acoustic Sensor) to join the Communications and Electronics (COMELEC) department.

This study is part of the "Ecoute Acoustique Terrestre" (EAT) RAPID (Dual Innovation Support Scheme) project, the result of a partnership between the company Febus Optics and Télécom Paris.

Distributed acoustic vibration measurement by optical fiber (DAS, Distributed Acoustic Sensing) is a recent technology with ever-diversifying applications. Examples include intrusion detection in perimeter surveillance, seismic measurements, well diagnostics (oil, geothermal), etc. The measurement bandwidth, from sub-Hertz to hundreds of kilohertz, also allows for audio band capture, and thus audio measurements over an optical fiber. It is thus possible to use the telecom optical network of a building for eavesdropping, by using a modified DAS system, incorporating specific material artifacts (winding, antennas, connectors) in the vicinity of the listening area and specific signal processing to achieve sufficient performance.

The framework of this Postdoc is to evaluate the vulnerability of a telecom network against potential eavesdropping by DAS. Connecting to an operational local telecom optical network requires adaptation to its architecture, particularly in terms of wavelength plan.

The audit of telecommunication systems to assess their vulnerability is a major issue for telecom networks. An example of an access network configuration is described in the figure below. From the Backbone network, starting from the 'Central Office', telecom signals are routed to subscribers via the PON (Passive Optical Network). Within buildings, a FTTX (Fiber To The X=Home, X=Room, X=Office, etc.) network or an optical LAN (Local Area Network) respectively carry the optical signal to the final terminal or communicate between two local terminals via an optical link. The PON includes a Feeder Fiber and then at least a 1×N coupler. Information coding is then a mix of coarse wavelength division multiplexing (C-WDM) and time division multiplexing (TDM). Each output port of the 1×N coupler is sent to groups of 1 to n subscribers through at least one filter that selects the wavelength allocated to them. The signal after this filter is then monochromatic and TDM coded. The final 1×n coupler distributes the signal to the n subscribers. This PON therefore includes, among other things, passive couplers that split signals to different subscribers, but also connectors, splices, etc.

The objective of this Postdoc is to take stock of the different types of networks in place and to evaluate their consequences on DAS measurement capability:

· Description of the different types of existing local networks,

· Overview of the different transmission types: CWDM, TDM, etc.

· What are the different access points for DAS measurement?

· How to discriminate between the different fibers interrogated after a coupler? Influence of reflective points,

· Study of the different power margins for DAS measurement,

· Potential presence of insertion nodes and limit of optical transparency,

· Sensitivity of DAS measurements depending on different fiber types and their environment,

· Influence of the final reflector on listening capacity.

The innovative aspect will be the definition of network conditions, configurations, and DAS performance allowing for a cyber audit of already deployed infrastructures.

Beyond a synthesis of configurations found in the field, it will involve conducting tests, either on a real network to which access will be granted, or on a model network implemented for the study. This work will allow for the identification of the necessary interface module types, their specification, and then their design and fabrication.

Your main responsibilities will be:

• Conduct research missions in the field of distributed fiber optic sensors

• Provide supervision and mentoring

• Contribute to the reputation of the School, Institut Mines-Télécom, and Institut Polytechnique de Paris

You hold a doctorate in electrical engineering, optical communications, photonics, optical sensors, or a related field. You have solid theoretical and practical expertise in photonics and digital signal processing, as well as good programming skills. Knowledge of signal processing algorithms applied to communication systems or fiber optic sensors, particularly in the context of coherent detection, is an asset. You are proficient in English, and proficiency in French is desired.

You have a strong interest in applied research and are able to thrive in a multicultural environment. You are comfortable supervising interns or students on projects. Finally, you demonstrate good teamwork, interpersonal, writing, and teaching skills, as well as excellent analytical and synthesis abilities.

Why join us?

You will work in a rapidly developing, pleasant, green, and accessible environment (especially for people with disabilities), just 20 km from Paris (RER B and C, proximity to major roads, shared shuttle from Porte d'Orléans). You will benefit from:

• 49 days of annual leave (paid leave + RTT)

• flexible working hours (depending on service activity)

• teleworking 1 to 3 days/week possible

• 75% reimbursement of public transport pass

• Proximity to numerous sports facilities, concierge service, underground parking, on-site catering...

• Good to know: our social contributions are lower than in the private sector

Miscellaneous information:

Application deadline: November 30, 2026

Job type: 12-month Fixed-Term Contract
Job description here

Our recruitment is based on skills, without distinction of origin, age, gender identity, and sexual orientation, and all our positions are open to people with disabilities.

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