OFDR Optical Frequency Domain Reflectometer

- Feb 28, 2019-

OFDR Optical Frequency Domain Reflectometer

 

The optical frequency domain reflectometer OFDR is a high-resolution optical fiber measurement technology that was gradually developed in the 1990s. Different from the optical time domain reflectometer OTDR transmitting into the system is the pulse signal in the time domain. The OFDR is transmitted into the system by using the narrow-band laser and the acousto-optic modulator to generate the swept optical signal, and then passed the optical heterodyne detection technology. A specialized algorithm to analyze the detected signal. Regardless of structure or algorithm, OFDR is more complex than OTDR.

 

OFDR Optical Frequency Domain Reflectometer


Introduction to OFDR

 

The optical frequency domain reflectometer OFDR is a high-resolution optical fiber measurement technology that was gradually developed in the 1990s. Different from the optical time domain reflectometer OTDR transmitting into the system is the pulse signal in the time domain. The OFDR is transmitted into the system by using the narrow-band laser and the acousto-optic modulator to generate the swept optical signal, and then passed the optical heterodyne detection technology. A specialized algorithm to analyze the detected signal. Regardless of structure or algorithm, OFDR is more complex than OTDR.

 

OFDR compared to OTDR

 

Compared with the well-known OTDR, the OFDR mode has higher sensitivity under the same environmental conditions. Under the same dynamic range, the required light source optical power is smaller, which can effectively overcome the spatial resolution and signal-to-noise ratio dynamics of the OTDR. Contradictions between the scope. The spatial resolution of OFDR is inversely proportional to the bandwidth of the receiver, and the noise is proportional to the bandwidth of the receiver, so the signal-to-noise ratio of OFDR can be made very high. The dead zone for OTDR measurement events is typically around tens of meters, while OFDR can reach micrometers. OTDR is generally used for long-distance fiber optic cable network testing to approximate the engineering faults, while OFDR is generally used for high-precision detection applications in access networks and sensing systems.

 

The composition and key technologies of OFDR

 

The key technologies of the OFDR system mainly include a linear swept source consisting of a narrow linewidth single longitudinal mode laser and an electro-optic modulator (usually an acousto-optic modulator), and an optical path composed of a MZ interferometer (including a coupler, a polarization controller, etc.) Requires the optical path to be as short as possible), optical path reception (balanced photodetector), data acquisition and algorithms.

 

OFDR product development

OFDR is currently a state-of-the-art technology product, and the only internationally known supplier is LUNA (www.lunainc.com) in Virginia, USA. However, the company's annual sales are less than 400 million US dollars, OFDR is only a small part of the LUNA products. In 2015, there were Jiangsu Jingjiang Junlong and Shanghai Jiaotong University Dong Yi teacher, and Nanjing's Jiangsu Ande Optoelectronics Technology developed technology and products. Before that, AVIC Metrology Institute also had product development. Others are mostly laboratory products of schools and research institutes.

 

Market application prospects of OFDR

 

OFDR can play an important role in the fault detection of fiber access networks, demodulation of high-precision temperature and stress sensing systems for aviation, and optical fiber sensing demodulation in medical applications. The successful application of this product relies on the development of smaller, more stable and higher precision OFDR products.