CANOGA PERKINS 2270 Fiber Optic Modem - Manual (Page 12)

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Canoga Perkins
•
Are you using the correct clock mode (internal/external) for synchronous trans-
mission?
•
Have the modem's mode and rate switches been set properly? (The 2270 is set to the
external clock mode at the factory.)
•
If you have problems after carefully checking these items, turn to Chapter 5, "Trouble-
shooting."
1. 9 Sensitivity and Optical Power Switches (HP Laser
Version Only)
A dual-section switch block is located between the transmit and receive optical connectors (see
Figure 1-3). The section nearest the transmit connector controls the optical transmit power level.
The section nearest the receiver controls the receiver sensitivity. For both switch functions, ON
selects HI and OFF selects LO. For standalone modems, ON = UP and LO = DOWN; for rack
mount modems, ON = RIGHT and LO = LEFT. This feature is only required for the HP laser fiber-
optic version. These switches are not provided in the other fiber-optic versions.
1. 9.1 Optical Power Switch (HP Laser Version Only)
The Optical Power Switch (TX POWER) provides two settings for optical transmission levels. The
LO switch setting is intended for use with short fiber optic lengths, i.e., a cable and connector
power loss total of less than 10 dB. The HI switch setting is intended for longer cable runs, up to
the maximum power loss budget.
1. 9.2 Sensitivity Switch (HP Laser Version Only
The Sensitivity Switch (RX SENS) provides two settings for optical receiver sensitivity. The LO
switch setting is intended for short fiber lengths in conjunction with LO optical power at the other
end. The LO setting must be used with a fiber link loss of 5 dB or less.
1. 9.3 Optical Switch Settings (HP Laser Version Only)
The proper setting of the Optical Transmit Power and Optical Receive Sensitivity Switches are
based on the loss measured on the fiber at a wavelength of 1300 nm. The 2270 should be used as
an optical power source when performing these measurements.
The loss on the fiber link determines the setting of the Tx Power Switch at the transmitting end and
the Rx Sensitivity Switch at the receiving end. It is important to remember that the switch settings
are determined separately for each fiber in the pair.
When operating the modem at rates above 6 Mbps, the HI/HI setting can always be used. HI/HI
refers to HI Tx power and HI Rx sensitivity. If the modem is to be operated below 6 Mbps, or if the
application requires full rate agility (without changing switch configuration) that extends below 6
Mbps, then the settings listed below should be followed.
TX PWR RX SENS MIN LOSS MAX LOSS
LO LO 0 5
LO HI 5 10
HI LO 10 13
HI HI 13 15