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:

                                                                                  

Ordering information

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