903-0628-00 Rev. 1
Model 903-HD User's Guide – FMB-X-2.5
Focal Technologies Corp.
Page 5-4
Figure 5-2 shows an LC connector which is a small form-factor fiber optic connector that uses a
1.25 mm ferrule and incorporates a push-and-latch design similar to an RJ-45 connector. Figure 5-3
shows an ST fiber optic connector that uses a 2.5 mm ferrule. The ST connector is latched into place
by twisting to engage a spring-loaded bayonet socket.
Ferrule
Figure 5-2: LC connector
Ferrule
Figure 5-3: ST Connector
4. Maintain good optical connections
Ensure connectors are well secured in the bushing and are not side loaded.
Never clamp down on fiber. For example, when securing the fiber to a PCB, do not use a tight
string, clamps or any mechanical means to tightly bind the fiber. Local stress on the fiber
increases loss and may break the fiber. Hard epoxies should also be avoided when securing
fibers on a PCB.
Never use the fiber to pick up or support the weight of the device to which it is attached.
Follow ESD guidelines for handling electrostatic sensitive devices, such as cards with electro-
optical devices.
SFP optical transceivers typically have a transmit and receive optical bushing (LC type), which
requires dual fiber operation. The transmit side (Tx) and the receiver side (Rx) of an SFP is
shown in Figure 5-4.
Tx
(Optical
Output)
Rx
(Optical
Input)
Figure 5-4: SFP Transceiver
5. Maintain proper optical power levels
Optical receivers will experience errors if the received optical power is too low. Ensure the total optical
losses of the components in the external cable system (jumpers, cable, connectors, couplers, FORJ,
etc.) are less than the specified optical power budget of the Model 903 system used. A calibrated optical
power meter should be used for any detailed measurements or trouble-shooting.
Optical receivers can also saturate and experience errors if the received optical power is
too high
,
especially when using high power transceivers. Use a 5 or 10 dB fixed attenuator in line with each fiber
during bench tests or with short, low loss links to ensure a minimum level of attenuation is present. A
variable optical attenuator (VOAT) can also be used for testing. In some high power systems, receivers
can actually be damaged by excessive optical power, so a fixed attenuator is recommended even with a
VOAT.
Summary of Contents for Focal 903
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