Telecast CopperHead 3400, Руководство пользователя

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Telecast Fiber Systems – CopperHead 3400 Transceiver System User Guide – Preliminary Version
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6.5.Using the Digital Displays
A Brief Guide to Measurement of Fiber Optic Signal Strength
Certain portions of this description are attributed to Wikipedia – The Free Encyclopedia.
The CopperHead 3400 Transceiver System provides direct digital readout of the Fiber Optic Link signal
strength for both the Base Station to Camera Unit Fiber Link and the Camera Unit to Base Station Fiber
Link. This readout is presented in units of dBm. It is useful to understand both the dB or decibel and the
dBm or decibel referenced to one milliwatt.
The decibel (dB) is a logarithmic unit of measurement that expresses the magnitude of a physical
quantity (usually power or intensity) relative to a specified or implied reference level. Since it expresses
a ratio of two quantities with the same unit, it is a dimensionless, relative unit. A decibel is one tenth of
a bel, a seldom-used unit. Typically dB has been employed in Audio Measurement and Fiber Optics
among many uses.
Proper measurement of signal strength requires an absolute measurement and the dBm provides this
measurement. Since it is referenced to the milliwatt, it is an absolute unit, used when measuring
absolute power. By comparison, the decibel (dB) is used for quantifying the ratio between two values,
such as signal-to-noise ratio
The CopperHead 3400 Transceiver System operates within a defined range of Fiber Optic Link signal
strength. The minimum recommended signal strength is -22 dBm or better. Typically the system should
operate at levels between -8 dBm and -20 dBm. The standard CopperHead 3400 laser output strength is
-6 dBm. Cable length affects signal strength as does the number of connections between the Camera
Unit and the Base Station. For example, using a Power Supply such as the MPS or HDX produces a
minimal signal loss through each connection.
The digital readouts on both the CopperHead 3400 Base Station and Camera Unit provide direct signal
strength measurements in dBm. These readouts also provide a wide range of diagnostic information.
The use of the digital readouts is described below
The CopperHead 3400 Base Station Digital Display
The Base Station digital display has three functions selected by the Display Mode Selector (#14 on the
Overview Diagram). These functions are indicated by the Display Mode LEDs.
1. BASE RX – Base Station Optical Power or Signal Strength that is being generated at the Base
Station and sent to the Camera Unit. Displayed in units of –dBm.
2. CAM RX – Optical Power or Signal Strength generated by the Camera Unit as measured at the
Base Station. Displayed in units of –dBm.
3. DIAG – One of four diagnostics modes available to the Base Station
a. TEMP – displays operating temperature in degrees Centigrade of each circuit board that
reports temperature
b. POWR – displays power level from monitored circuit boards
c. REV – displays microcontroller firmware version from each circuit board with a
microcontroller
d. CAM – displays the error status reported by the Camera Unit