A Low-Cost, System-on-Chip for Optical Time
Domain Reflectometry (OTDR)
Jingbo Shi
1
, Nan Qi
1
, Qianqian Yang
1
, Hui Guo
1
, Guangyao Yang
2
, Jiangbing Du
2
, Qingwen Liu
2
, Zuyuan He
2
, Rui
Bai
3
, Patrick Yin Chiang
1,4
, Zhiliang Hong
1
1
State Key Laboratory of ASIC and System, Fudan University, Shanghai, 201203, China
2
State Key Laboratory on Intelligent Photonics, Shanghai Jiao-Tong University, Shanghai, China
3
PhotonIC Technologies, Shanghai, China
4
Oregon State University, Corvallis, OR, USA
Email: jingboshi@fudan.edu.cn
Abstract—A single-chip Optical Time Domain Reflectometer
(OTDR) system-on-chip (SoC) for fiber-optic fault detection
and localization is presented. The IC can be configured into
several modes including high-performance mode (external
modulator and expensive off-chip laser / APD), and low-cost
mode (low power/gain and inexpensive laser / APD).
Experimental optical measurements demonstrate that the
maximum detectable fiber length of the proposed OTDR SoC
can be as long as 25km, while the spatial resolution can
achieve 2.5m, 4m and 10m, for various configurations.
Compared with current discrete solutions on the market, the
proposed OTDR system can reduce the cost by 100x, area by
5x, and power consumption by 4x.
Keywords—Optical time domain reflectometer (OTDR); low
cost OTDR; fiber length dection; optical fiber sensor; optical fiber
insert loss; transimpedance amplifier; laser; APD.
I. INTRODUCTION
With the rapid development of modern communications
and insatiable demand for data, the Passive Optical Network
(PON) represents one of the most attractive access solutions
due to its high bandwidth provisioning ability [1, 2]. Fig.1
illustrates a common usage scenario for a PON, consisting of a
large number of fiber splitters, Optical Network Units (ONUs),
and Optical Network Terminals (ONTs), designed to exchange
data between the center office and the user in several ways,
such as fiber-to-the-curb (FTTC), fiber-to-the-node (FTTN),
fiber-to-the-premise (FTTP) and fiber-to-the-home (FTTH).
Due to the large number of passive fiber connections, and
susceptibility to optical fiber misalignment and poor coupling,
the Optical Time Domain Reflectometer (OTDR) has been
widely used to both sense and diagnose PON fiber quality,
capacity, and performance in real-time.
The realization of an OTDR system for diagnosing a fiber
network can achieved by monitoring the Fresnel Reflection and
Rayleigh Backscattering that occur along the fiber [3-5]. Fig.2
shows the principal scheme for the Fresnel Reflection and
Rayleigh Backscattering, which are used to diagnose the length
and insertion loss of the fiber, respectively.
The maximum distance of fiber length and the spatial
resolution are critical factors for evaluating an OTDR’s
performance. The former can be derived by setting the
backscattered power equal to the input referred noise:
=⋅⋅⋅=
−∂
ητ
(1)
where P
0
is the effective launch power of the laser pulse
(actual power launched into the fiber multiplied by the
Fig.1 Block Diagram of a PON System
Fig.2 The Scheme for Fresnel Reflection and Rayleigh Scattering
,(((