Model 250S1G6
Rev D
13
2.6.3
Fiber-Optic Serial Communication
The Fiber-Optic port is a serial communications bus. All commands and queries through this port must be
terminated with a Line Feed character. When a valid query is received, it is processed and the result is
immediately transmitted back over the Fiber-Optic interface. This port is designed to time-out if there is no
activity on the bus for more than 5 seconds. At this time the internal buffer is cleared and a
TIMEOUT_ERROR
message followed by a Line Feed is sent out from this port.
The baud rate for the Fiber-Optic Serial port is user selectable from the RS-232/Fiber-Optic Serial Baud Rate
selection screen. To get there from the Main Menu, touch the User menu button followed by the I/O menu
button and finally the Serial menu button. A thin black outline indicates the present baud rate selection.
When the back button is pushed, the baud rate selection is stored to non-volatile memory. Therefore, if power
is lost prior to hitting the back button, any baud rate selection changes will be lost.
NOTE: This baud rate setting is shared by both the Fiber-Optic serial port and the RS-232 port.
The Fiber-Optic port provides the user with the ability to optically isolate the controlling PC from the
amplifier. This can be useful in an environment where RF/Microwave energy could be coupled onto a
connection to one of the “wired” communications ports and fed back to the controlling PC.
Both optical connections (TX and RX) are optimized to work with light at a wavelength of 820nm. For more
detailed specifications on this port, consult the Avago HFBR series datasheet found at
A glass, multi-mode, fiber-optic cable of 200um is recommended, however fiber-optic cable as small as 50um
can be used. The connector type for this port is ST.
This port can be used in conjunction with either an AR model IF7000 RS-232 to Fiber-Optic Interface (1200
to 9600 baud only) or an AR model IF7001 USB to Fiber-Optic Interface (19200 baud only). Note that these
devices use SMA connectors so a fiber-optic cable is needed with ST connectors on one end and SMA
connectors on the other. This cable can be obtained from a fiber-optic cable distributor such as Fiber
Instrument Sales (FIS). Their web-site can be found at
. An example cable
that will work for this connection is FIS Part Number D615M7FIS. The 7 in the part number refers to the
length of the cable. In this case the length is 7 meters.
Table 2-3. Fiber-Optic Serial Port Settings
Word Length
8 bits
Stop Bits:
1
Baud Rate:
User selectable (default is 19200)
Parity:
None
HW Handshake:
None
2.6.4
USB Communication
The USB port is a USB 2.0 port. It also complies with the USB Test and Measurement Class (USBTMC)
Standard. Communications with this port requires the host computer to have a USBTMC driver available.
All commands and queries through this port must be terminated with a Line Feed character.
The cable required to make this connection is a USB 2.0 A-B peripheral device cable. The cable can be no
longer than 5 meters. If a longer distance is required a USB hub must be used. A cable carrying the official
USB logo is recommended.
