CN1716825A - Mobile communication digital optical fiber direct distribution station using daisy chain driving structure - Google Patents

Abstract

The present invention discloses a kind of digital optical fiber direct laying station series for the daisy chain transmission structure. The way of the digital optical fiber transmission is used between the relay terminal and coverage terminal; the upper link uses the way of daisy chain series while the lower link uses the way of wideband coupler series. Both the relay terminal and coverage terminal comprise radio frequency transreceiver, modulation/demodulation, AD/DA, base band processing, optical transmission and reception, supervision and control and power source. The datum station signals of the down-link chain circuit are sent to base band I/Q or changed into lower-medium frequency signals through the lower frequency conversion, then transformed into digital signals and baled into serial data, which through optical fiber transmission and coupling one by one, will be sent to various distant terminal machines where through frame demodulation, the digital signals will be restored to I/Q or lower-medium frequency, again changed into analogue signals and finally through the upper frequency conversion, sent onto radio frequency and realized the distant coverage. The I/Q data of the later grade distant terminal machines for the upper-link chain circuit will be sent to the previous grade after piling up. The overall piling-up signals will be sent up to the datum stations through the above reverse process. The invention only requires a single pair of optical fiber to complete the distant transmission of digital optical fiber signals through multi-channel carrier and can realize great dynamic signal coverage with big capacity.

Description

Adopt the mobile communication digital optical fibre repeater series of daisy chain transmission structure

Affiliated technical field

The present invention relates to a kind of mobile communication distant signal covering system, be specifically related to a kind of mobile communication digital optical fibre repeater series that adopts the daisy chain transmission structure, adopt the digital fiber transmission means between its relay and the capped end, up link adopts daisy chain serial connection mode, and down link adopts wide-band coupler serial connection mode.

Background technology

The basic demand of present mobile communication system can not have been satisfied user's demand, optimizes and improve the referred important schedule of service, and the radio network optimization and the network coverage show its importance just day by day.Wherein, direct discharging station is the low and characteristics in increase coverage territory rapidly with cost of investment that it was had, have become an indispensable part in radio network optimization and covering.Direct discharging station is divided into outdoor repeater and indoor repeater.The former mainly comprises: wireless discharging-directly station, optical fiber repeater, multiband frequency-shift repeater etc.; The latter is also referred to as indoor distributed system, mainly comprises radio frequency transmission mode, Optical Fiber Transmission mode and electric light mixed transport mode etc.Incompatible to choose suitable covering scheme be one of important topic of the network optimization according to different geographical environments and applied field, many high-level wireless coverage total solution have appearred at present, but still there are many technical problems that need to be resolved hurrily, as in traditional transmission means and coverage mode, just there are the limited problem of dynamic range in the remote covering of its signal and linear covering, are difficult to satisfy the long-distance transmissions of multi-carrier signal and the actual needs that remote linear terrain signal covers.

Summary of the invention

The purpose of this invention is to provide a kind of mobile communication digital optical fibre repeater series that adopts the daisy chain transmission structure, to solve the existing the problems referred to above in traditional approach repeater, realize the long-distance transmissions and the big capacity of multi-carrier mobile communication signal, the signal of great dynamic range covers, for mobile communication system increases flexibly a kind of, the new technique means that great dynamic range and jumbo radiofrequency signal long-distance transmissions and linear landform cover, the list that is applicable to three sectors or many sectors is to Optical Fiber Transmission and covering, the list of the many sectors of single carrier is to Optical Fiber Transmission and covering, and the list of many sectors and multicarrier is to Optical Fiber Transmission and covering.

The present invention covers terminal subsystem 102 by near-end repeater subsystem 101 and far-end and constitutes to 105.Its near-end repeater subsystem 101, far-end cover and adopt the digital fiber transmission means between the terminal subsystem 102,103,104,105, up link adopts daisy chain structure serial connection mode, and down link adopts wide-band coupler 106,108,109 serial connection modes; Its each subsystem is formed by radio-frequency receiving-transmitting subsystem, modulating/demodulating subsystem, ADC/DAC subsystem, baseband, light transceiver subsystem, Monitor And Control Subsystem and power subsystem.Its system work process is: at down link, its GSM, CDMA, WCDMA, the cdma2000 base station signal is down converted to baseband I/Q or Low Medium Frequency signal, transform to digital signal again, and it is packaged into serial data by certain frame format, through optical transceiver, by Optical Fiber Transmission to corresponding coupler, and be coupled to corresponding remote termination by its coupling port, the output port of its coupler then continues to be transmitted through the fiber to next coupler also by that analogy, cover the terminal subsystem at far-end, its serial data signal is separated frame revert to I/Q or Low Medium Frequency signal, transform to analog signal again, upconvert to radio frequency at last and send to the overlay area; In up link, to cover to continuity terminal n+1 and be connected to covering terminal n, to cover terminal n and be connected to covering terminal n-1, thereafter the I/Q data of level far-end covering terminal subsystem are delivered to the prime far-end again and are covered the terminal subsystem also by that analogy after corresponding levels stack, and its total superposed signal is by delivering to the base station on the above-mentioned inverse process.

Adopt the transmission of digital fiber transceiver between described near-end repeater subsystem and far-end capped end loom system, it is to adopt Ethernet protocol that its typical case uses; The A/D of described ADC/DAC subsystem and/the typical figure place of D/A is 12bits, can change into 10bits, 14bits, 16bits respectively according to different system; The speed of the serial digital signal of uplink and downlink fiber optical transceiver and optical fiber link can be designed to respectively according to practical application request: 614.4Mbps, 1228.8Mbps, 2457.6Mbps.

Described baseband comprises relay, base station baseband processing module and far-end capped end baseband processing module.

Wherein, the course of work of relay, base station baseband processing module is: the downstream signal of base station is sent into baseband processing unit 307 after A/D306 is transformed into digital signal, the data chainning of the data chainning of this signal and webmaster is merged together sends into 8B/10B encoder 308 after forming specific frame format, the data-signal of baseband processing unit 307 being sent here by encoder 308 carry out 8B/10B error detection, go to send into fiber optical transceiver 309 behind direct current, the coding, be sent to far-end through optical fiber and fiber coupler then and cover terminal; Cover the terminal stack and next serial high speed uplink digital signal by all far-ends, receive and send into 8B/10B decoder 308 through fiber optical transceiver 309, carry out error detection and data frame format recover after with its data parallel send into baseband processing unit 307, to revert to I/Q data and webmaster HDLC interface data, I/Q data are wherein sent into and are sent after D/A converter groups 312 becomes it into analog signal.

The course of work of its far-end capped end baseband processing module is: from branch's high-speed downstream digital signal of relaying terminal 101 or wide-band coupler, after fiber optical transceiver 316 receives, send into 8B/10B decoder 318 and carry out error detection and data frame format recovery, and with its parallel baseband processing unit 319 of sending into, data are reverted to the HDLC interface data of I/Q data and webmaster, and I/Q data are wherein sent into and are sent after D/A converter groups 320 becomes it into analog signal; , send into A/D converter groups 327 and become digital signal after down-conversion from the upward signal of portable terminal, the baseband I/Q data of the back level far-end that receives at baseband processing unit 319 and optical receiver 317 superpose, and form total I/Q data.Carry out framing again from the input signal frame of webmaster HDLC interface at the corresponding levels and the webmaster HDLC interface input signal frame of back level far-end, form a total HDLC signal frame.These two total I/Q data and total HDLC signal frame form the data-signal that is fit to CPRI protocol frame structure, carry out error detection, remove direct current, send into fiber optical transceiver 316 behind the coding by 8B/10B codec 318 then, with data serial deliver on the optical fiber.

Described daisy chain transmission structure uses single to optical fiber serial connection far-end covering terminal, be that far-end covering terminal at the corresponding levels utilizes the daisy chain connected mode to be connected with adjacent with it far-end covering terminal by optical cable and by that analogy, its far-end covers terminal 1 and is connected with the near-end repeater by optical cable.

Expressed intact formula according to signal:

In the formula, a=rcos , b=rsin ,

Adopt following vector addition formula to carry out the signal stack:

$\stackrel{\&RightArrow;}{X_0}\left(f\right)=\stackrel{\&RightArrow;}{{\mathrm{<figure-callout\; id="1"\; label="X"\; filenames="A20051009027300111.png"\; state="\{\{state\}\}">X</figure-callout>}}_1}\left(f\right)+\stackrel{\&RightArrow;}{X_2}\left(f\right)+\&CenterDot;\&CenterDot;\&CenterDot;+\stackrel{\&RightArrow;}{X_n}\left(f\right)$

$=(a_1+{\mathrm{jb}}_1)+(a_2+{\mathrm{jb}}_2)+\&CenterDot;\&CenterDot;\&CenterDot;+(a_n+{\mathrm{jb}}_n)$

$=(a_1+a_2+\&CenterDot;\&CenterDot;\&CenterDot;+a_n)+j(b_1+b_2+\&CenterDot;\&CenterDot;\&CenterDot;+b_n)$

The stack of carrying out amplitude at numeric field in transmission course, only need the consistency of maintenance amplitude, and phase information is to be determined by the correlation of I and Q, so can not destroy original information; Wherein, the I/Q data of capped end at the corresponding levels and the I/Q data of last capped end merge by the FPGA mode at baseband processing unit, be that the digital amplitude addition merges, but not Digital Logic merge.The upward signal of near-end relaying terminal is the stack of whole capped end upward signals, and the upward signal that far-end covers terminal n+1 then is the direct signal from portable terminal of not stack.Its a ₁+ a ₂+ ... + a _nAnd b ₁+ b ₂+ ... + b _nExtraction solve by spectrum-spreading address code, by the Base-Band Processing of base station and portable terminal, can with the stack Signal Separation come out.

The downstream signal of far-end mulch-laying machine 1 is from the near-end repeater, and the downstream signal of far-end mulch-laying machine 2 to n+1 is from the serial high-speed downstream branch digital signal of previous stage wide-band coupler.The selection of described wide-band coupler is flexibly, but must satisfy the requirement of power output.Between the wide-band coupler also can be apart from di in conjunction with autonomous selection of concrete condition (as geographical environment etc.), but the principle of following be make transmission of wireless signals distance farthest, the area coverage maximum.Wherein, following formula is followed in the concrete calculating of fibre loss:

$P_{\mathrm{outn}}=\mathrm{Pin}-\mathrm{\&alpha;}\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}\mathrm{di}-\underset{i=1}{\overset{n-1}{\mathrm{\&Sigma;}}}\mathrm{\&Delta;i}-\mathrm{Ln},$

$P_{\mathrm{out}0}=\mathrm{Pin}-\mathrm{\&alpha;}\underset{i=1}{\overset{n+1}{\mathrm{\&Sigma;}}}\mathrm{di}-\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}\mathrm{\&Delta;i}$

Wherein α is the decay db/km of optical fiber unit, and Ln is the degree of coupling, and Δ n is an Insertion Loss, and di is a distance.

Brief Description Of Drawings

Figure 1 shows that the system block diagram of the mobile communication digital optical fibre repeater series of employing daisy chain transmission structure provided by the present invention;

Figure 2 shows that system's composition diagram of near-end repeater subsystem provided by the present invention;

Figure 3 shows that the system composition diagram of far-end mulch-laying machine 1 provided by the present invention to the n subsystem;

Figure 4 shows that system's composition diagram of far-end mulch-laying machine n+1 subsystem provided by the present invention.

Its description of reference numerals is as follows:

101: the relaying terminal; 102,103,104,105: far-end covers terminal; 107,310,315,328,341: optical fiber; 106,108,109,110,302: coupler; 303: duplexer; 304,324,336:RF module; 111,301: the base station main antenna; 112,314: antenna is assisted in the base station; 306,327,338:A/D converter; 307,319,331: baseband processing unit; 313,322,333: modulator; 305,323,337: demodulator; 309,316,340: optical transceiver; 317: optical receiver; 308,318,330:8B/10B conversion; 312,320,332:D/A converter; 311,321,339: synchronous circuit; 325,326,334,335: the capped end antenna.

Embodiment

Below in conjunction with accompanying drawing, describe the specific embodiment of the present invention in detail.

1, referring to the system block diagram of the mobile communication digital optical fibre repeater series of employing daisy chain transmission structure shown in Figure 1.

As shown in the figure, near-end repeater 101 is finished the obtaining and sending of base station signal through coupler 110, and far-end covers terminal 102～105 and finishes obtaining and sending the mobile phone signal through antenna feeder.Wherein, near-end repeater and far-end cover the fiber optical transceiver that adopts ethernet standard between the terminal and pass through optical fiber 107 and realize that digital signals transmit; Up link adopts daisy chain structure serial connection mode; Down link adopts wide-band coupler 106,108,109 serial connection modes.At down link, its GSM, CDMA, WCDMA, cdma2000 base station signal are down converted to baseband I/Q or Low Medium Frequency signal, transform to digital signal again, and it is packaged into serial data by certain frame format, through optical transceiver, by Optical Fiber Transmission to the far-end wide-band coupler, by wide-band coupler signal is divided into two-way, one the tunnel to far-end covering terminal 1, another road passes toward farther next wide-band coupler (acting on the same), so signal can one direct transfers and covers terminal to far-end more until last.Cover the terminal subsystem at far-end, its serial data signal is separated frame revert to I/Q or Low Medium Frequency signal, transform to analog signal again, upconvert to radio frequency at last and send to the overlay area.In up link, to cover to continuity terminal n+1 and be connected to covering terminal n, to cover terminal n and be connected to covering terminal n-1, thereafter the I/Q data of level far-end covering terminal subsystem are delivered to the prime far-end again and are covered the terminal subsystem also by that analogy after corresponding levels stack, and its total superposed signal is by delivering to the base station on the above-mentioned inverse process.So just finish the far-end covering function of mobile communication base station, constituted the pull system far away of base station.

2, referring to system's composition diagram of near-end repeater subsystem shown in Figure 2.

The down link course of work of this subsystem is: the near-end repeater will be fed into duplexer 303 from the mobile communication downlink signal of base station main antenna 301 by coupler 302, through RF module 304, by demodulator 305 it is down-converted to baseband I/Q or Low Medium Frequency signal, be transformed to digital signal through A/D converter 306 then, by baseband processing unit 307 it is packaged into serial data by certain frame format, is transferred to the far-end capped end through optical transceiver 309 by optical fiber 310 again.Its up link be will come from up resultant signal after all far-end capped ends stacks, the inverse process of the down link by above-mentioned near-end repeater presents up radiofrequency signal to the base station.

3, referring to the system composition diagram of far-end mulch-laying machine shown in Figure 31 to the n subsystem.

From branch's high-speed downstream digital signal of relaying terminal 101 (for covering terminal 1) or wide-band coupler (for covering terminal 2～n), receive through fiber optical transceiver 316, and by 8B/10B codec 318 carry out error detection and the decoding after, separate frame by baseband processing unit 319, it is reverted to I/Q data-signal and webmaster HDLC interface data signal respectively, i/q signal wherein is by 12bits (or 10bits, 14bits, D/A converter groups 320 16bits) is transformed into analog signal with it, behind modulator 322, deliver to RF (radio-frequency module) 324 again, be emitted to the overlay area via antenna 325 at last.

From the upward signal of portable terminal after RF (radio-frequency module) 324 receives, by demodulator 323 with its down-conversion, by A/D converter groups 327 it is transformed to 12bit/s (or 10bit then, 14bit, digital signal 16bit), and superpose at baseband processing unit 319 with signal from all back level capped ends of optical receiver 317, then this signal with form the data-signal that is fit to CPRI protocol frame structure from the input signal of webmaster HDLC interface, then carry out error detection by 8B/10B codec 318, remove direct current, the coding back forms high-speed serial digital signal, transmits it to the near-end repeater by fiber optical transceiver 316 by uplink optical fibers link 315 at last.

4, referring to system's composition diagram of far-end mulch-laying machine n+1 subsystem shown in Figure 3.

Branch's high-speed downstream digital signal of wide-band coupler, receive through fiber optical transceiver 340, and by 8B/10B codec 330 carry out error detection and the decoding after, separate frame by baseband processing unit 331, it is reverted to I/Q data-signal and webmaster HDLC interface data signal respectively, i/q signal wherein is by 12bits (or 10bits, 14bits, D/A converter groups 332 16bits) is transformed into analog signal with it, behind modulator 333, deliver to RF (radio-frequency module) 336 again, be sent to the overlay area by antenna 334 at last.

Upward signal from portable terminal, earlier through demodulator 337, by A/D converter groups 338 it is transformed to 12bit/s (or 10bit, 14bit again, digital signal 16bit), this signal and the input signal from webmaster HDLC interface are formed the data-signal of suitable CPRI protocol frame structure by baseband processing unit 331, then by 8B/10B codec 330 carry out error detection, remove direct current, the coding back forms high-speed serial digital signal, by uplink optical fibers link 341 it transferred to repeater 101 by prime covering terminal by fiber optical transceiver 340 at last.

Claims (7)

1, a kind of mobile communication digital optical fibre repeater series that adopts the daisy chain transmission structure, covering terminal subsystem (102) to (105) by near-end repeater subsystem (101) and far-end constitutes, it is characterized in that, near-end repeater subsystem (101), far-end cover and adopt the digital fiber transmission means between terminal subsystem (102), (103), (104), (105), up link adopts daisy chain structure serial connection mode, and down link adopts wide-band coupler (106), (108), (109) serial connection mode; Its each subsystem is formed by radio-frequency receiving-transmitting subsystem, modulating/demodulating subsystem, ADC/DAC subsystem, baseband, light transceiver subsystem, Monitor And Control Subsystem and power subsystem; At down link, its GSM, CDMA, WCDMA, the cdma2000 base station signal is down converted to baseband I/Q or Low Medium Frequency signal, transform to digital signal again, and it is packaged into serial data by certain frame format, through optical transceiver, by Optical Fiber Transmission to corresponding coupler, and be coupled to corresponding remote termination by its coupling port, the output port of its coupler then continues to be transmitted through the fiber to next coupler also by that analogy, cover the terminal subsystem at far-end, its serial data signal is separated frame revert to I/Q or Low Medium Frequency signal, transform to analog signal again, upconvert to radio frequency at last and send to the overlay area; In up link, to cover to continuity terminal n+1 and be connected to covering terminal n, to cover terminal n and be connected to covering terminal n-1, thereafter the I/Q data of level far-end covering terminal subsystem are delivered to the prime far-end again and are covered the terminal subsystem also by that analogy after corresponding levels stack, and its total superposed signal is by delivering to the base station on the above-mentioned inverse process.

2, the mobile communication digital optical fibre repeater series of employing daisy chain transmission structure according to claim 1, it is characterized in that, adopt the transmission of digital fiber transceiver between described near-end repeater subsystem and far-end capped end loom system, it is to adopt Ethernet protocol that its typical case uses; The A/D of described ADC/DAC subsystem and/the typical figure place of D/A is 12bits, can change into 10bits, 14bits, 16bits respectively according to different system; The speed of the serial digital signal of uplink and downlink fiber optical transceiver and optical fiber link can be designed to respectively according to practical application request: 614.4Mbps, 1228.8Mbps, 2457.6Mbps.

3, the mobile communication digital optical fibre repeater series of employing daisy chain transmission structure according to claim 1 is characterized in that, described baseband comprises relay, base station baseband processing module and far-end capped end baseband processing module.

4, relay, the base station baseband processing module of the mobile communication digital optical fibre repeater series of employing daisy chain transmission structure according to claim 3, it is characterized in that, the downstream signal of base station is sent into baseband processing unit (307) after A/D (306) is transformed into digital signal, the data chainning of the data chainning of this signal and webmaster is merged together sends into 8B/10B encoder (308) after forming specific frame format, the data-signal of baseband processing unit (307) being sent here by encoder (308) carries out the error detection of 8B/10B, remove direct current, send into fiber optical transceiver (309) behind the coding, be sent to far-end covering terminal through optical fiber and fiber coupler then; Cover the terminal stack and next serial high speed uplink digital signal by all far-ends, receive and send into 8B/10B decoder (308) through fiber optical transceiver (309), carry out error detection and data frame format recover after with its data parallel send into baseband processing unit (307), to revert to I/Q data and webmaster HDLC interface data, I/Q data are wherein sent into and are sent after D/A converter groups (312) becomes it into analog signal.

5, the far-end capped end baseband processing module of the mobile communication digital optical fibre repeater series of employing daisy chain transmission structure according to claim 3, it is characterized in that, branch's high-speed downstream digital signal from relaying terminal (101) or wide-band coupler, receiving and send into 8B/10B decoder (318) through fiber optical transceiver (316) carries out after error detection and data frame format recover, with its parallel baseband processing unit (319) of sending into, data are reverted to the HDLC interface data of I/Q data and webmaster, and I/Q data are wherein sent into and are sent after D/A converter groups (320) becomes it into analog signal; Upward signal from portable terminal, after down-conversion, send into A/D converter groups (327) and become digital signal, the baseband I/Q data of the back level far-end that receives at baseband processing unit (319) and optical receiver (317) superpose, and form total I/Q data; Carry out framing again from the input signal of webmaster HDLC interface at the corresponding levels and the webmaster HDLC interface input signal of back level far-end, form a total HDLC signal frame, then, these two total I/Q data and total HDLC signal form the interface frame form that is fit to the CPRI agreement and send into error detection that 8B/10B encoder (318) carries out 8B/10B, go to send into fiber optical transceiver (316) behind direct current, the coding, with data serial deliver on the optical fiber.

6, the mobile communication digital optical fibre repeater series of employing daisy chain transmission structure according to claim 1, it is characterized in that, its described daisy chain transmission structure uses single to optical fiber serial connection far-end covering terminal, be that far-end covering terminal at the corresponding levels utilizes the daisy chain connected mode to be connected with adjacent with it far-end covering terminal by optical cable and by that analogy, its far-end covers terminal 1 (102) and is connected with the near-end repeater by optical cable;

Expressed intact formula according to signal:

In the formula, a=rcos , b=rsin , $r=r=\sqrt{a^2+b^2},$

Adopt following vector addition formula to carry out the signal stack:

$\stackrel{\&RightArrow;}{X_0}\left(f\right)=\stackrel{\&RightArrow;}{X_1}\left(f\right)+\stackrel{\&RightArrow;}{X_2}\left(f\right)+\&CenterDot;\&CenterDot;\&CenterDot;+\stackrel{\&RightArrow;}{X_n}\left(f\right)$

$=(a_1+j{b}_1)+(a_2+j{b}_2)+\&CenterDot;\&CenterDot;\&CenterDot;+(a_n+j{b}_n)$

$=(a_1+a_2+\&CenterDot;\&CenterDot;\&CenterDot;+a_n)+j(b_1+b_2+\&CenterDot;\&CenterDot;\&CenterDot;+b_n)$

The stack of carrying out amplitude at numeric field in transmission course, only need the consistency of maintenance amplitude, and phase information is to be determined by the correlation of I and Q, so can not destroy original information; Wherein, the I/Q data of capped end at the corresponding levels and the I/Q data of last capped end merge by the FPGA mode at baseband processing unit, be that the digital amplitude addition merges, but not Digital Logic merge; The upward signal of near-end relaying terminal is the stack of whole capped end upward signals, and the upward signal that far-end covers terminal n+1 (105) then is the direct signal from portable terminal of not stack; Its a ₁+ a ₂+ ... + a _nAnd b ₁+ b ₂+ ... + b _nExtraction solve by spectrum-spreading address code, by the Base-Band Processing of base station and portable terminal, can with the stack Signal Separation come out.

7, the mobile communication digital optical fibre repeater series of employing daisy chain transmission structure according to claim 1, it is characterized in that, the downstream signal of far-end mulch-laying machine 1 (102) is from the near-end repeater, and the downstream signal of far-end mulch-laying machine 2 (103) to n+1 (105) is from the serial high-speed downstream branch digital signal of previous stage wide-band coupler; The selection of described wide-band coupler is flexibly, but must satisfy the requirement of power output; Between the wide-band coupler can be in conjunction with selecting apart from di such as concrete conditions such as geographical environment are autonomous, but the principle of following be make transmission of wireless signals distance farthest, the area maximum of covering; Wherein, following formula is followed in the concrete calculating of fibre loss:

$P_{\mathrm{outn}}=P_{\mathrm{in}}-\mathrm{\&alpha;}\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}\mathrm{di}-\underset{i=1}{\overset{n-1}{\mathrm{\&Sigma;}}}\mathrm{\&Delta;i}-\mathrm{Ln},$

$P_{\mathrm{out}0}=P_{\mathrm{in}}-\mathrm{\&alpha;}\underset{i=1}{\overset{n+1}{\mathrm{\&Sigma;}}}-\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}\mathrm{\&Delta;i}$

Wherein α is the decay db/km of optical fiber unit, and Ln is the degree of coupling, and Δ n is an Insertion Loss, and di is a distance.

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