return path
these wide changes in drive without clipping. The change in signal
level that a transmitter can tolerate is known as the dynamic range.
The RPT 3105-BTN achieves a dynamic range of 15 dB, more than
sufficient for most applications.
Also, the Fabry-Perot lasers used in other transmitters are very noisy
when not modulated. Transmitters using these lasers must always
modulate the laser with a carrier, which greatly decreases the
dynamic range. The DFB laser used in the RPT 3105-BTN
maintains nearly the same low noise even when not modulated.
This is important in the return path, where burst data is common.
Advantages
"High performance, uncooled DFB laser.
"High dynamic range for immunity to ingress.
"User-selectable to either 2 mW (+3 dBm) or 1 mW (0 dBm)
optical output allows optimizing optical power for a wide range
of optical links.
"Stabilized to maintain performance over the operating
temperature range.
Applications
"Pay-per-view
"Network management communications
"Telephony
"Internet data
Return Path Transmitter
HL 3000 Series
Product Description
Harmonic’s RPT 3105-BTN return transmitter addresses the need
for a high-performance transmitter for the General Instrument
BTN and Mini Bridger optical nodes. The transmitter is based on
an uncooled Distributed Feedback (DFB) laser. This laser has much
lower noise and better distortions than the Fabry-Perot laser used in
other transmitters for these nodes.
The transmitter features a novel optical power circuit which allows
the output power to be set to either 2 mW (+3 dBm) or 1 mW
(0 dBm). This allows a single transmitter to be used for both longer
and shorter optical links.
The RPT 3105-BTN has outstanding video and data performance.
It contains a unique thermal compensation circuit which maintains
high performance over the entire operating temperature range.
As the return environment becomes noisy, and the noise level varies
dramatically, the laser in a return transmitter must be able to handle
RF Input
(35 dBmV)
24 VDC
Optical out
0 dBm(o) (19% OMI)
or +3 dBm(o)(10% OMI)
Clamp 32
32
Optical
power
control
Analog monitoring
and control section
Linear
Regulator 7 VDC Laser power select
[0 or +3 dBm(o)]
Optical power
test point (1 V/mW)
Optical power
monitor point (1 V/mW)
LED
(GRN-OK
RED-Low Opt. Pwr
OFF-Power OFF)
OMI adj. OMI temp comp.
Fixed
Pad xfmr
Plug-in
pad DFB laser
Standard Configuration
RPT 3105-BTN + RPT 3105-MBR
preliminary
RPT 3105-BTN + 3105-MBR
Preliminary Specifications
Copyright 1999 Harmonic Inc. Harmonic continues to improve and enhance all
product designs. Specifications are subject to change without notice. Harmonic
and logo design, eXchange, MAXLink, METROLink, NETWatch, PWRBlazer,
TRANsend, and “Redefining the Network” are trademarks of Harmonic Inc.
YAGLink and PWRLink are registered trademarks of Harmonic Inc. All other
names are trademarks or registered trademarks of their respective owners. 2322-03 2.5K 9/99
Harmonic Inc.
549 Baltic Way
Sunnyvale, CA 94089
Tel. 408-542-2639
Tel. 800-730-4099
Fax 408-542-2510
Optical Output
Laser type: Uncooled, isolated DFB laser
Output power:
+3 or 0 dBm (optical) (user-selectable via
jumper)
Tracking error: ≤± 1 dB(optical)
Connector type:
RPT 3105-BTN-US: SC/UPC
RPT 3105-BTN-AS: SC/APC
RPT 3105-MBR-AF: FC/APC
Wavelength: 1280-1350 nm
User Interface
Laser output power test point: 1 V/mW
Green LED: Power on
Red LED: Laser power low <0.5 mW
Element Management System - NETWatch™/HEM
Parameters available for monitoring: Laser output level
Power Requirements
Power supplied by node in which the transmitter is
mounted
Supply voltage: +24 VDC
DC current draw 3: 0.2 A (max.)
Environmental
Node internal temperature: –40˚ to 85˚ C/–40˚ to 185˚ F
Storage temperature: –40˚ to 85˚ C/–40˚ to 185˚ F
Physical
Dimensions: 5.5" L x 1.2" W x 1.2" H
14.0 cm L x 3.0 cm W x 3.0 cm H
Weight: 5 oz./0.14 kg
Mounting: Within General Instrument’s BTN or MiniBridger
nodes.
Notes:
1. Over the full temperature range; for 10-dB fiber loss and 10% OMI at +3 dBm (optical) output;
4 MHz bandwidth)
2.
At +3 dBm (optical) output; 5-45 MHz noise loading; 7 dBm (optical) fiber loss; at input to the module
3.
At 24 VDC; over full temperature range
Link Performance
CNR1: ≥49 dB
IMD21: ≤–52 dBc
IMD31: ≤–57 dBc
RF Input
Operational bandwidth: 5-65 MHz
Frequency response: ≤1.5 dB (elec.) (peak-to-valley, 5-65 MHz)
RF input return loss: ≥18 dB
RF attenuator: 0 to 10 dB in 1 dB steps
Impedance: 75 Ω
Connector type: Type “F” connectorized pigtail
Analog:
Nominal RF input into the module for 10% OMI at +3 dBm
(optical) output: 35 dBmV (plug-in pad set to 9 dB)
Nominal RF input into the module for 19% OMI at 0 dBm
(optical) output: 35 dBmV (plug-in pad set to 9 dB)
Digital:
Nominal input RF power spectral density for C/(N+I) = 40 dB
2
:
–45 dBmV/Hz
Input RF dynamic range for C/(N+I) = 40 dB
2
: 14 dB
-60
10
15
20
25
30
35
40
45
-55 -50 -45 -40
RF Input, dBmV/ Hz
* 8 dB Optical Link, 40 MHz Data Loading.
S/(N+I), dB
-35 -30 -25 -20
Noise Power Ratio*
