1550nm External modulation transmitter use DFB low-chirp laser with optical isolator,47-28 work bandwidth,18-28dBmV input level.

HHTX-1550 1550nm transmitter External modulation CATV optic fiber:
Important technology data:
Performance Index Supplement
Optic feature Wavelength range (nm) 1555��5 ITU-TG.692 Standard wavelength
Line width (MHz) ?1 FWHM(��)
Side mode suppression ratio (dB) ?45 SMSR
Equivalent noise intensity (dB/Hz) ?-160 RIN (20~1000MHz)
Output power (dBm) 2��7 Optional 2��5, 2��6, 2��9, 2��10
Return loss (dB) ?50
Optical fiber connector SC/APC Optional LC/APC,FC/APC
RF feature Work bandwidth (MHz) 47-862
Input level (dBmV) 18~28 AGC
Flatness (dB) ?��0.75 45~862MHz
Return loss (dB) >16 45~750MHz
Input impedance (��) 75
RF port F-Female
Link feature Transmit channel PAL-D/60CH NTSC/80CH
CNR1 (dB) ?53 Back to back
CNR2 (dB) ?52 65Km optical fiber, 0dBm receive
CTB (dBc) ?-65
CSO (dBc) ?-65
SBS restrain (dBm) 13, 16, 18 Adjustable
General feature Network interface port RJ45, RS232 Support I.E. & SNMP
Power supply (V) 110~220VAC -48VDC optional
Power Consume (W) ?50 Single power works
Work temp. () -5~65 Machine temp. control automatically
Storage temp. () -40~85
Operating relative humidity (%) 5~95
Housing Dimensions (mm) 19��14.5��1.75 (W)x(D)x(H)


If you want to transmit more than 100km, you need to select 13dBm SBS restrain status. Why you need to do this is because of SPM & optic fiber Chromatic Dispersion. If bandwidth-extending status is not changed, when fiber length is longer, CSO performance will be worse. If you want to choose longer distance transmission, you need to select smaller line bandwidth. 13dBm is much smaller, 16dBm is much bigger, and 18dBm is the biggest. The following table shows the recommended fiber length in which SBS restraint status.

Optic Fiber Length SBS Restrain Condition
60Km 13dBm, 16dBm, 18dBm
70Km 13dBm, 16dBm
120Km 13dBm
120Km 13dBmCSO performance will be some different from the specification possibly

The biggest optic fiber Input power is restricted by SBS restraint status. If your power is bigger than the stipulated limit, it will occur some bad result. The low frequency band will have 1/f noise, low channels CNR will not be good, HUM will also be worse than in normal status. The attached table shows the limit value of SBS restraint power.
SBS restraint power Limit of optic fiber input power
18dBm Max.18.4dBm
16dBm Max.16.4dBm
13dBm Max.13.4dBm

The general CATV operator will use high power EDFA (such as 22dBm and higher one), and use optic splitter to arrange the power transmitting in the optic fiber & cable. It is no problem to do this, because the optic fiber patch cord is short. But it is necessary to notice that SBS restraint setup rest with the worse situation, for example, the longest distance & the biggest fiber input power in the optic cable.