INFORMATION

Description

     The external modulated transmitter is
specially developed for the CATV signal that satisfies HFC network, and the
long-distance transmission of cable phone and cable data.This optical transmitter is a 1550nm DFB laser. The external modulated transmitter can be managed by console or WEB managed, easily mornitor and configure.

Working principle

It has 7 function modules:
RF control, DFB laser, optical modulator, SBS control, CSO control,
communication/display control and power supply.

Automatic gain control
circuit (AGC) or manual gain control circuit (MGC) amplifies the RF signal. AGC
or MGC control makes the optical modulator maintain a suitable input level. Use
the detected RF root-meansquare(RMS)-total
power to calculate the optical modulation index(OMI).

In general we
recommend using the AGC function, and special users can use the MGC function to
adjust the CNR/CSO/CTB performance indexes.

    The core of transmitter is
the optical modulator. The 1550nm signal input the optical modulator, make the
laser intensity changed follow the external RF signal voltage, and then
generate the AM optical signal.   

Stimulated Brillouin
Scattering (SBS) occurs, when the optical input power is greater than a certain
threshold value. SBS generate the lower frequency backscattered light which
will attenuate the transmission light and return to the laser while destroying
its performance. Causing optical power fluctuation, generates large noise, and
seriously deteriorates the system carrier to noise ratio (CNR). To improve the
SBS threshold, this optical transmitter adopts SBS control technology which is
independent researched and developed by ourselves. The threshold value can be
set up to 19dBm.

    The
optical modulator has a two-way optical signal output. Parts of that signal are
routed to an InGaAs photodiode. This detection of the optical signal has two
functions:

  1) Detect whether the laser is
normal working. Once the output optical power is 2dB lower than standard power,
alarm will be set off.

  2) Detect CSO distortion to
optimize the bias point of the optical modulator. For working normal the
detector circuit needs at least two carrier signal inputs with an interval of
24MHz. There is a CSO initialization program in the boot
process. If the CSO install failed, the RF indicator
will flash red, see details in 6.2
Troubleshooting.

 

Block Diagram

1.3 Product
Applications

• High-performance
long-distance transmission

• High-power distribution
network

• Redundancy loop
architecture

• FTTx network

• RFOG application

• DWDM network

 Technique Parameters
Optical Parameters

Item	Unit	Value
Optical Wavelength	nm	1545～1560 (or specified by the user)
Side-mode Suppression ratio	dB	>30
Relative Intensity Noise	dB/Hz	<-160
Wavelength Adjustment Range	GHz	+/-50GHz
Optical Power	dBm	2*5, 2*7, 2*8, 2*9, 2*10
SBS Threshold Value	dBm	+13～+19 (Continuously adjustable)
Laser Linewidth	MHz	0.3

Technical Specification

Item	Unit	Technical Parameters
RF range	MHz	47～1003
RF flatness	dB	+/-0.75
RF return loss	dB	>16
RF input impedance	Ω	75
RF input connector type		F type
Rated input level	dBμV	80
Input level range	dBμV	78~96 (AGC mode, modulating signal)
AGC control range	dB	+3～-3
MGC adjustable range	dB	0~15
Optical connector		SC/APC, FC/APC
Operating temperature	°C	-5～45
Storage temperature	°C	-30～+70
Power Source Specification	V	90～265VAC
		36～72VDC
Consumption	W	≤60
Dimension	mm	483(L) × 455(W) × 44(H)
Total Weight	kg	5.5

Panel Interface and Menu System Description

Front Panel

1	Power indicator	2	AGC indicator	3	RF modulation degree indicator
4	Laser indicator	5	LCD	6	ESC key
7	UP key	8	DOWN key	9	Enter key
10	RF input port (or on the rear panel, optional)	11	-20dB RF input test port

 

Rear Panel

1	Ground stud	2	Power module	3	Fan
4	RF input port (or on the front panel, optional)	5	RS232 interface	6	LAN interface
7	Optical output interface A (or on the front panel, optional)	8	Optical output interface B (or on the front panel, optional)

Power Module

220V Power Module

1	Mounting screws	2	220V power outlet	3	Fuse
4	Power switch

48V Power Module

1

Mounting screws

2

+ Positive terminal block

3

– Negative terminal block

WEB Network Management

Open the IE
browser, type the IP address and enter the interface as follows: