BLOCK DIAGRAM & OPERATION
5-2
ChromaFlex DMT24, DMT34 & DMT44 Multi-Wavelength DWDM Direct Modulated Transmitter Module – Hardware Interface Manual
Input 1
(*-1)
Input 2
(*-2)
Input 3
(*-3)
Input 4
(*-4)
Variable
Attenuator
Variable
Attenuator
Variable
Attenuator
Variable
Attenuator
RF Det.
RF Det.
RF Det.
RF Det.
ITU*
ITU*
ITU*
ITU*
Opt. Mux
Front Panel
Test Point - 10 dB
OUT 1
OUT 2
OUT 3
OUT 4
DMT44
* = card
number (1..8)
Figure 3: ChromaFlex DMT44 Transmitter Module Block Diagram
As seen in the block diagrams above and as described in Product Introduction, the DMT24 and DMT34 have internal RF
combining to merge a common broadcast RF input signal to each individual NC input. The DMT44 has no such combining
since all four rear F-ports are utilized for direct application to each laser segment in the quad module. After this initial
combining stage, all transmitter versions have the same functionality.
A directional coupler for each laser segment provides a sample of the full spectrum RF load applied to each laser to the
switchable female F-port on the front. This level is calibrated to be -10 dB relative to the input at the rear of the module,
regardless of AGC function of the module. The RF signal passes through a variable RF attenuator. The attenuator is
either automatically set through the feedback loop when operated in the AGC mode or may be set in the manual mode via
software interfaces. The signal is amplified and then passes through a directional coupler used to sample the RF signal for
remote monitoring and the AGC control loop back to the input variable attenuator. The through path is applied to a laser.
Fiber length adjustment for the laser is set through the software interfaces. The optical signal passes to each of the front
panel optical connectors. An internal multiplexer option is available in which case each wavelength is multiplexed internally
with the combined wavelengths connected to output port 1.
CHAPTER 5:
