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Digital Fiber DAS

DAS Stone 132℃

Digital fiber DAS ( fiber optical repeater) adapts SDR (software digital radio) technology to digitize the GSM Um interface signal, transfers to the remote unit via the optical cable, and then uses the remote RF unit to regenerate, amplify the signal to cover the remote target area.

Basic Principles

Digital fiber optical repeater MU(main unit) couples the BTS downlink signal; then the signal passes the duplexer, frequency converter module, A/D converter module, FPGA and optical module. In frequency converter module, the RF signal converter into IF (intermediate-Frequency) signal; the IF signal is converted into digital signal by A/D converter and do digital down converter; then the digital signal is processing by FPGA to realize signal channelized of different mobile network standard, auto gain control, auto noise cancelation and to operate CPRI agreement. In optical module, the digital signal converts to optical signal and transmits to RU via optical fiber. In contrast, the signal is deal with the same way, to convert the signal from optical signal to RF signal. Then the RF signal is amplified by amplifier and LNA module and transmitted to antenna. It is the same way to deal with the uplink signal and to return the signal to BTS.

In the whole process, there is no interaction between the digital signal transmission and the optical transmission, so that the digital signal does not attenuate with the attenuation of the optical signal, and the wireless signal path loss between the base station and the repeater is canceled. Long-range high-speed transmission, can still maintain a high dynamic range, to ensure signal quality, maximize the use of spectrum resources and network equipment, the equivalent of a base station and mobile phone provides a two-way transparent channel, then the wireless signal has been extended.

Block Diagram

Main Technical Parameters

GSM Selective Band Digital Fiber Optical Repeater Main Parameters

  • Max. Output Power: Uplink10W:40dBm±2;Downlink:20W:43dBm±2-10dBm±2
  • Noise: Uplink:No Need ; Downlink:≤3dB
  • Optical Transmission Distance:20Km
  • Spurious Emission:≤-36dBm/30kHz;9KHz-1GHz≤-36dBm;1-12.75GHz≤-30dBm
  • Power Supply:170VAC~270VAC,–40VDC~–60VDC
  • Power Consumption:MU 40Wmax,RU 100Wmax
  • Emit Optical Wave Length:MU1550 nm /RUlink1-1310nm,link2-1550nm
  • Output Optical Power:-3dBm~-8dBm
  • Input Optical Power:>-20dBm
  • Max. Gain:Uplink 50±2dB;Downlink 50±2dB
  • Manual Gain Control: Uplink:31dB;Downlink:31dB
  • Gain Adjust Step: Uplink:1dB;Downlink: 1dB
  • Gain Adjust Error:≤±1.5dB
  • ALC:At Max. Out power , raise extra 10dB,out power change is less than 2dB


Digital fiber optic repeater can realize multi-channel parallel, multi-channel series ,daisy chain and other networking methods, can greatly save fiber optic cable resources, make the system more flexible.

Technical Features

  • Adapt CPRI compliant transmission interface, and apply digital optical technology
  • The RF signal does not attenuate with the attenuation of the optical signal, keeping the dynamic range constant in long distance and multi-path shunt systems.
  • Transmission error rate is less than 10exp-12
  • Use the software radio method to digitize the RF signal. Processing the signal in the digital domain greatly enhances the device’s processing and control of the signal.
  • To track the processing of each carrier frequency, each time slot signal, completely eliminate the uplink noise interference
  • Digital filtering has better rectangular coefficients than acoustic surface filters
  • Full support EDGE
  • Achieve good uplink and downlink lever balance by adapting uplink noise control technology


  • Traffic statistics for each time slot
  • Independent service for each remote
  • Scheduled by default time
  • According to the detection of each actual traffic to schedule

Product & Components Structure

MU Structure and Internal Structure

Digital fiber optical Main Unit is made up of digital IF board, frequency converter module, monitor panel, modem, optical transceiver, power supply module, fans, access control switch and so on.

Structure Diagram
MU Assemble Diagram

RU Structure and internal structure

Digital fiber optical repeater remote unit consist of IF module, frequency converter module, integrate amplifier module, optical module, power module, fans, access control switch.

RU Structure and internal structure

Module Introduction

Digital fiber optical repeater mainly consist of digital IF board, integrated amplifier module, frequency converter module, monitor module, optical module, power supply module and so on.

Digital IF Board

  • The digital IF board converts the signal between analog IF signal and digital signal and achieve d the function such as: AGC, auto noise cancelation, GPRI agreement operation.
Digital IF Board Interface diagram

Digital IF board interface and function description

1.JP407\JP409:Power Input
Pin2,4:Ground connection
2.JP405\JP404\JP406:RS485 Port,connect engineer computer, monitor board
Pin1:B Cable
Pin 2:A Cable
Pin 3:Ground connection
3.JP410/JP411:RS485 Port,connect module
Pin1:B Cable
Pin2:A Cable
4.JP412:Reserved Detection Port
5.JP403:CPU software download Port
JP600:FPGA Simulation Interface
JP601:FPGA Software download interface
6.F904:Optical Link1 connect fiber optical
F903: Optical Link2 connect fiber optical
F902: Optical Link1 connect fiber optical
F901: Optical Link1 connect fiber optical

7.P300:AD input,76.8MHZ,IF input,Connect frequency converter module
P500:122.88MHZ detect interface
P502:DA output,61.44MHZ IF output, connect frequency convert module
P503:Reference Frequency output, connect frequency convert module
8.LED indicator explanation:
MU:FD1、FD2、FD3、FD4 Normally on,Indicate Link1,2,3,4 Sync. state
FD5 Normally on
FD6、FD7 Normally off
FD8 Flash,CPU Operating indicator
RU:FD1、FD2 On,indicate link 1,2 Sync. state
FD3 Off
FD4 On,PLL state indicate
FD5、FD6、FD7 Normally on
FD8 Flash,CPU operating indicator

Integrate Amplifier Module

  • The integrate amplifier module divided into LNA, and downlink amplifier. The downlink amplifier is to do linear amplifier the downlink signal power. As for the large power and produce much heat, it sets in horizontal installation.
  • The integrate amplifier module includes 4 RF interfaces, 2 power supply interfaces(9V and 27V), 1 local RS232 interface, 4 location holes.
Integrate Amplifier Module

4 RF Interface Descriptions:
PA-IN: RF input
PA-OUT:RF output
LNA-IN:Lower Noise Amplifier signal input
LNA-OUT:Lower Noise Amplifier signal output;
RS232 External Descriptions:
RS232 external interface is mainly used to link the
the monitor board and amplifier module. Then it is to
check the module status .

Frequency Convert Module

This module converts the RF signal to analog IF signal.

Monitor Board

Monitor Board adapts core board and plate board structure. Integrate CPU, FLASH, DRAM, CLOCK in the core board. It is the core part in the monitor. The plate board is made up of power supply unit, external interface, button and button battery.

Monitor Board

NO. Button Description
1 K1 Start Report
2 K2 Recheck Report
3 K3 Software Reboot
4 K4 Configure change report
5 K5 Alarm restore report
6 K1 Combine K2 Software upgrade report
7 K4 combine K5 Login Control Center Report
8 K1 Combine K5 Heart Beat Report
9 K2 Combine K4 Finish Report
10 K1 Combine K4 Restore Default

Parameter & Value

  • Max. Gain & error
  • Max. Gain ≤113dB,based on the request;
  • Max, Error :Less than ±3dB。
  • Manual Gain Control
  • MGC ≥30dB
  • MGC Step length and error
  • MGC step length≤2dB;
  • Error less than ±1dB/step,±1dB/(1-10dB),±1dB/(10-20dB),±1.5dB/(20-30dB)。
  • Frequency error
  • Frequency error :Single unit is less than±5×10-8 ,System is less than±1×10-7。
  • EVM error
  • EVM(RMS):≤6%(root –mean-square)
  • Max. input electronic Level
  • Wireless couple repeater RF input port:
  • Max. input electronic level ≥-10dBm
  • Direct couple repeater input port:
  • Max. input electronic level ≥10dBm

Pass Band Ripple

Pass band ripple ≤3dB(Peak-peak value)

Input and output VWSR


Out-band Rejection

Out-band Rejection

Operating band intermodulation index:

Noise Figure
-Single Unit:At Max. and min. Gain state(GMAX-15dB):NF≤5dB
-Chain Networking: At Max. Gain NF≤5dB
-Star Networking: At Max. Gain NF≤7dB
As to direct couple to BTS, the forward amplifier NF no need

Send and receive isolation
As repeat send and receive isolation is les 10dB than the max. Gain. It meets 8PSK EVM≤6%(rms). It ensures repeater don’t do self oscillation.
Transmission Delay
Single Unit:≤10μs(wireless repeater)、≤18μs(fiber optical repeater)
Transmission Delay adjust scope
Delay Scope≥100μs
Delay error
Less than ±3μs
In-band Carrier Leakage Suppression
In-band carrier leakage per useful carrier >60dB。
Under the interference signal, the repeater gain reduces is not less <6dB.

  • Uplink Noise suppression
  • Start the device, uplink Noise suppression ≤-96dBm/30kHz
  • Close and start the device, the noise level difference is less than 17dB
  • With different carrier and different time slot, separate control feature
  • Noise level suppression threshold can adjust, the scope ≥30dB,step≤2dB;
  • The max. threshold is less -108dBm/200kHz。
  • Input RF Range
  • The input signal scope:≥40dB or the min. scope≤-90dBm,EVM deteriorate is less 6%.

Application &Analysis

Application 1:Solving urban residential area coverage (IBS)

As to some residential areas, there are high requirements for the coverage, and adapts fiber DAS. Fiber DAS cuts down the cost of the feeder in main line ,linkage loss, and the device quantity; it also improves the coverage quality.

Fiber DAS

Application 2:Scenic spot wireless coverage solution

As to scenic spot, fiber DAS can provide good wireless coverage solution to these areas.

1.Integrated Cabinet

2. Application Diagram

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