Detector documentation in PDF form: Datei:Detector Module.pdf‎

Synopsis

This module is designed to provide configurations of photodetectors for heterodyne detection. It is responsible for reading and recording the data that is returned from the atmosphere to the system (1).

Glossary of Terms

1. InGaAs: Indium Gallium Arsenide

Design Requirements

This section includes the objectives and constraints of the Detector module (2).

1. Must be sensitive in the given range of optical wavelength

  a. Should be constant or well defined within some wavelength range 

2. Must be suitable for the range of optical power

3. Should have high quantum efficiency

Safety

This section describes the safety concerns of the Detector module, and suggestions for mitigating any possible risks.

The safety concerns of the detector module center around the chance of incoming radiation being redirected into the eyes of a bystander. As such, any radiation paths throughout the module must be completely sealed from the outside world. This includes both the backscattered path and the local oscillator’s path. In addition to this, all power outlets must be insulated and sealed, in order to prevent any accidental contact to high voltages by operators of the system.

High Level Overview

This section will discuss the main functions of the Control module and its constituent components.

Figure 1: System diagram of the Detector module

The detector module is separated into two major categories, the InGaAs Photodetector and the Photodetector Circuit. The photodetector circuit is only used if an amplifier is needed.

Low Level Information

This section includes an overview of the electronic components and circuitry that may be used in the detector module.

All information is specific to a single brand of InGaAs photodetector, and is simply a suggestion for the model of detector to use in the final design.

InGaAs Photodetector (JDSU (3)):

-Active diameter: 100µm -Responsivity: 0.75A/W -Dark current: 0.30A -Capacitance: 1.1pF -Bandwidth: 1.5GHz -Rise time: 250ps 

Photodetector circuit:

-InGaAs Photodetector -Amplifier -Bandwidth: 2GHz 

The use of photodetector circuit instead of an InGaAs photodetector alone has an advantage. It reduces parasitic capacitance, which allows the detector to operate on a wider laser bandwidth (4).

Interfaces

Figure 2: Dependency Map of Detector module; details in Table 1

Inputs	Outputs
Power – Power to operate the sensors and electronics	Control – Data to be processed by the Internal Control
Optics/Scanner – Local oscillator beam – Backscattered beam

Table 1: Inputs and outputs of Detector module

Progress

This module is currently in the abstract definition phase.

Testing

Type description of testing on module here.

Comments

Software and power diagrams should be created as needed.

Detector module colour (Hex code): #666666

Revision History

Description of Work	Date	Author
Document started	27.07.15	Alan Yeh
Added High Level Overview, Low Level Overview, System Diagram, Dependency Map, Interfaces	27.07.15	Alan Yeh
General edits to grammar and style	31.07.15	Joshua Calafato, Katherine Maul, Frank Modruson IV, Alan Yeh
Added References	2.08.15	Alan Yeh
Minor format edits	12.08.15	Frank Modruson IV

References

1. How does LiDAR works? (2015). In Lidar-UK.com. Retrieved August 2, 2015 from http://www.lidar-uk.com/how-lidar-works/

2. Photodetectors. (n.d.). In RP-Photonics.com. Retrieved August 2, 2015 from http://www.rp-photonics.com/photodetectors.html

3. High Speed InGaAs Photodetector Receptacle Modules. (2012, May 1). In JDSU.com. Retrieved August 2, 2015 from http://www.jdsu.com/ProductLiterature/etx100-ds-oc-ae.pdf

4. Koch, G., Beyon, J., Barnes, B., Petros, M., Yu, J., Amzajerdian, F., . . . Singh, U. (2007, November 20). High-energy 2μm Doppler lidar for wind measurements. In Opticalengineering.Spiedigitallibrary.org. Retrieved August 2, 2015 from http://opticalengineering.spiedigitallibrary.org/mobile/article.aspx?articleid=1088598