The figure is a simplified diagram of a relatively inexpensive controller for a DiCon VX (or equivalent) fiber-optic switch — an electromechanically actuated switch for optically connecting one or two input optical fibers to any of a number of output optical fibers. DiCon VX fiber-optic switches are used primarily in research and development in the telecommunication industry. This controller can control any such switch having up to 32 output channels.
A digital input/output (I/O) interface circuit is needed for controlling the switch and reading its status. This controller was developed as an alternative to the control interface suggested by the manufacturer of the switch. The manufacturer provides a schematic diagram of an interface circuit that utilizes the parallel port of a personal computer, and provides sample software for use with the interface. However, the parallel ports on some personal computers are not compatible with the interface suggested by the manufacturer. In contrast, the present controller uses a standard RS-232 serial interface, which is available on most computers and can ordinarily be utilized with less difficulty than can a personal-computer parallel port.
The heart of this controller is a commercially available microcontroller that includes 16 digital I/O ports and flash memory that can hold up to 1KB of program. The controller also includes an RS-232 driver. Two of the digital I/O lines are used for serial communication, via the RS-232 driver, between the microcontroller and the personal computer. Nine of the digital I/O lines are used for controlling the switch and reading its status. One of the digital I/O lines is used to control the power to the switch through a relay, and two of these lines are used to drive a two-color light-emitting-diode (LED) front-panel display. The software enables a user to interactively control the switch by means of simple commands and to monitor the responses of the switch. The front-panel display enables the user to determine the status of the switch ("busy" or "error") at a glance.
The serial-port architecture of this controller facilitates establishment of an interface between this controller and commercially available laboratory automation software. It is also possible to connect this controller to a universal serial port via an appropriate converter. Therefore, the switch can be controlled by a variety of computers, without need for expensive digital I/O boards or complicated programming.
This work was done by Robert Peters of Caltech for NASA's Jet Propulsion Laboratory.
This Brief includes a Technical Support Package (TSP).
Alternative Controller for a Fiber-Optic Switch
(reference NPO-43306) is currently available for download from the TSP library.
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Overview
The document outlines the development of an Alternative Controller for a Fiber-Optic Switch, specifically the DiCon VX fiberoptic switch, as detailed in NASA Tech Brief NPO-43306. The primary motivation for this development was to address compatibility issues between the DiCon fiberoptic switch and various computer hardware configurations, particularly concerning the parallel digital interface that was often incompatible with different operating systems and PC hardware.
To solve this problem, the authors designed a simple, low-cost microcontroller-based device that utilizes the RS-232 serial interface for communication with computers. This approach is advantageous because the RS-232 interface is widely available on most computing platforms and is generally easier to work with than the parallel port interface. The core of the device is a Microchip microcontroller, which features 16 digital I/O ports and can store up to 1K of programming in its flash memory. The design incorporates a Maxim MAX232A driver for serial communication, along with several digital I/O lines dedicated to controlling the fiberoptic switch and providing status indicators.
The device allows users to interactively control the fiberoptic switch using a simple terminal program, enabling straightforward command input and response monitoring. Additionally, front panel indicators provide real-time status updates, enhancing user experience and operational efficiency. The architecture of the serial port also facilitates easy integration with lab automation software, such as National Instruments' LabVIEW, making it a versatile solution for various applications.
The document emphasizes the novelty of this approach, highlighting its cost-effectiveness and ease of use compared to previous methods that relied on more complex and expensive digital I/O boards. By utilizing a standard RS-232 interface, the new controller can be connected to a variety of computing platforms without the need for specialized hardware or complicated programming.
Overall, this Technical Support Package serves as a comprehensive overview of the alternative controller's design, functionality, and advantages, showcasing its potential for broader technological, scientific, and commercial applications beyond its initial aerospace context. The document also provides contact information for further inquiries related to research and technology in this area, emphasizing NASA's commitment to sharing innovative developments with the wider community.
