Chapter 6

136 159

6-1 General :- 6-1.1 Meters required for POI A/T. OFC Media,

1. Optical Power Meter any make for Trans power / Rx Sensitivity of OFC system 2. Optical Variable Attenuator any make for ----------do--------------of OFC system

Any of the following Network Analyzers for Return loss and cable attenuation:-

3. Anritsu Network Analyzer MS 3401 A 10 Hz-30 MHz with reflection bridge MA 2202 A and transformer 75/120.

4. HP Network Analyzer 8751 a 5Hz – 500 MHz with bridge. 5. AGILENT Network Analyzer E 5100 A 10 KHz -180 MHz

with AGILENT Trans/ Reflection Test set 87512 A and 75/120 transformer 6. W & G Network Analyzer PSM -137 with bridge.

Any of the following Testers for Pulse characteristics Test:- 7. ACTERNA E1 Service tester EST 125 DB -0760 8. HP digitizing oscilloscope No. 54503 , 500 MHz 9. AGILENT digitizing oscilloscope No.5430

Any of the following PDH/SDH Analyzers for BER, Jitter, Alarm test and Stability Test:-

10. Anritsu MP 1550 B PDH/SDH Analyzer or MP 1552 A 11. W & G ANT-20 E or ACTERNA ANT-20 SE 12. Meter no 7 13. ACTERNA E1 and DATA TESTER EDT – 135 14. BER Tester 9 Sunlight E1 by Sunlight Telecom.

Any of the following meters for frequency measurement:-

15 HP DTA set 37721 A 16 HP Universal frequency counter 53131 A/ 225 MHz 17 Anritsu frequency counter

Other Accessories:- 18. Printer for BER, Jitter mask printouts. 19. SC-FC, SC-PC, LC-FC Patch cords 20. Moligraph optical fibre cleaner 1/0402 or any other cleaner

POI (Point of interface) Acceptance Testing 6-1.2 Various Vendors :- At present the following vendors use to offer A/T from T & D Circle, they are:-

1. VSNL 2. Reliance communication ltd 3. IDEA 4. Bharti Airtel Limited 5. TTML 6. Hutch Vendor has to apply for nos. of E1 as required and paying for E1 as per BSNL norms

6-1.3 Before A/T :- . POI A/T use to offer in three types which are as follows :-

1. E1 interface A/T. 2. Traffic shifting from passive network to active network i.e. installation of STM-1

system. 3. E1 working on Copper cable with modem, as POP distance is more.

A/T starts from the verification of documents which are as follows: -

1. Offering memo 2. Payment details, Advice note, Demand note, 3. Paid receipt ACG-67 4. Circle representative nomination letter as a third committee member, 5. The trunking diagram of scheme.

Verify all relevant documents as above and find out any discrepancy in documents and bring to the notice of vendor. A/T should be carried in the following manner: -

1. Check of documentation. 2. POI Equipment A/T. 3. Stability of E1 on loop from vendors MSC. 4. A/T report signature and forwarding to DET A/T ( Trans ), informing completion

of A/T to DET A/T Switching to carry out POI Switching A/T.

POP OFC BSNL STM-1 STM-1

CU Cable BSNL POP

Fig. 6-1

137

6-2 Transmission A/T:- 6-2.1 Transceiver parameters :- The following OFC STM-1 Systems are being installed by Vendor.

1. Tejas 100 CP (8 E1) 2. ECI 3. Nortel

First of all check the physical installation of Rack, vertical support/runway at the top of the system, DC power supply distribution through MCB taken or not?

1. To check of Trans power of STM-1 system port-1 and port 2.Connect power meter to port 1 and measure the trans power of port 1 which should be as per following table. Measure trans power of 2nd port also.

2. Limits are as below :-

System Trans power Rec. Sensitivity

Overload

Tejas 100 CP S1.1 L1.1

-8 to -15 dBm 0 to -5 dBm

< -28 dBm <-28 dBm

-8 dBm -10 dBm

ECI -10 to -15 dBm <-33 dBm -13 dBm Nortel +2 to -5 dBm <-28 dBm -8 dBm

3. Receiver Sensitivity :- Prepare the set up of test as below Fig. 6-2.

DDF OF System

Keep Attenuator normally at -20 dBm and observe loop O.K on DTA set. Increase attenuation till you observe EC=1 on DTA set. Disconnect Rx of V/ Attenuator for and connect to power meter so as to get exact sensitivity point. Now go to higher side so as to observe EC=1 and note down the overload point. Repeat same procedure for port 2 also. 4. Check of alarms: - Check and indicate functioning of various audible/ Visual alarms provided on the system as follows :-

Patch cards V/ Attenuator

TX RX DTA Set

EC= 1 SES

Fig.6-2

138

a. Major b. Minor c. Critical For this alarm test , in the above Rx sensitivity set up, further increase attenuation gradually and observe Minor, Major, Critical alarm on system. e.g. In Tejas 100 CP system following are the Minor, Major and Critical alarm that you have to monitor. Minor : - 1. E -6 Major : - AIS, Signal degraded, Excessive Error Critical : - LOS, LOF. 5. Check of DDF: - Check that DDF is crone type or regular at PSTN end is provided ,it is inbuilt or wall mounted DDF. If not. then separate DDF should be provided , also verify that DDF is earthed or not? 6. Performance Stability: - After all POI A/T tests are over, System is ready for Stability test . Arrange loop from their nearest MSC, and confirm it by taking disconnection. If whole route is OFC up to their MSC then stability Period is 24 Hrs and any M/W media is involved in between the route, then Carry out stability for 96 Hours . Attach Print out with the A/T report. 7. Safety requirements: - All the equipments like Antennas, Tower, Mast/ pole, Feeder, RF equipment and accessories , check physically for their protection from lightning and similar hazards, also check OF cable, Feeder cable entering in the equipment room is properly protected/ covered/ sealed or not? Wave Guide is properly taken on runway or not? OF cable entry in BSNL MDF is protected or not? 6-2.2 ii. 2.048 Mb/S interface. Testing at POI 1. Check of attenuation of interconnecting cable: - By 5100 network Analyzer. Cu cable / PCM Cable connectivity: - Feed 1024 KHz at 0 dBm and measure O/P at distance end, calculate the loss which should not exceed 6 dB. 2. OF Cable Connectivity: - Generally vendor used to lay 6F or 12F OF cable for connectivity at PSTN end. OF cable is laid and maintained by them only. So need not to conduct A/T of all 6/12 F. Moreover as they are not offering whole cable for A/T, So only the fibers of interest viz F1, F2 on which system will work, are to be tested. Note down the Trans power of port-1 and port-2 by Power Meter. Go to vendor site with power meter ask PSTN end to send source power and measure Rx power calculate the fibre loss which is to be calculated as below as the distance is always <10 Km a. No. of splice x 0.1 = 2 x 0.1 =0.2 b. FDF loss 0.5 x 2 = 1.0 c. 0.38 x Cable length in Km = d. Total loss = a + b + c e. Limit for Cable loss = d dB/Km Length of cable

139

2. Return loss Measurement at input port (For passive link this test is to be taken) This is to be taken for impedance matching120 Ω between POI. End and vendor site.

A] With Agilent Network Analyzer 5100 A. Fig 6-3

Pulse

R A B RF OUT 75 Ω

HP 87512 A Bridge

75 Ω 75 Ω 75 Ω 120 E1 RX Transformer

Fig 6-3

Make a test set as shown in the above figure with Network Analyzer and bridge. This test can be carried out by Anritsu, HP, Agilent or by W/G Network Analyzer. Here all four meter’s set up is shown and explained, near about procedure is same for all set up except some extra operations of buttons. 1. Meas/format- log mag . 2. Calibration: - Connect Open/short and Load connector – done. 3. Select frequencies – start –enter 51 KHz – enter stop frequency 3072 KHz 4. Connect E1 Rx to bridge I/P port and a trace is displayed on screen. 5. Press marker key – select all required frequencies one by one and note Down the corresponding reading. B] Return Loss by Anritsu Network Analyzer. - Make a test set up as below Fig. 6-4. - Connect E1 Rx to 120 Ω put of bridge section enter start, - Enter start frequency 51 KHz and stop frequency 3072 KHz and observe trace on Analyzer display. - Press scale for offset A, move wheel to centre point= 0 dBm as O/P reference.

140

- Calibration X S ON( self calibration) enter - Select frequencies as per table either by wheel or by pressing soft keys. - Note down Return loss reading. - The reading set should be repeated for all offered E1,S. - Readings for example :- 51 KHz 13 dB 100 KHz 18 dB 400 KHz 24 “ 600 KHz 26 “ 600 “ 26 “ 1000 “ 27 “ 1500 “ 28 “ 2500 “ 28 ” 2600 “ 24 “ 3072 “ 18 ” Limits :- 51 – 102 KHz ≥ 12 dB 102 - 2048 KHz ≥ 18 dB 2048 – 3072 KHZ ≥ 14 dB Return loss with Anritsu Network Analyzer:-

Fig 6-4

WHEEL

E1 Rx

G

120 Ω 20 Ω

Anritsu Reflection

O/P 75 Ω Prob I/P 75 Ω

0 dB Max

Bridge MA2202 A

30 Hz-250 MHz

Bridge Section

Anritsu Reflection Bridge MA2202 A 30 Hz-250 MHz

Transformer Section

Bridge Section

8

Max.+20dB +12V source

O/P 75 Ω I/P 75Ω Prob +12V

141

Fig. 6-5

50 Ω50 Ω 50 Ω

Return loss with HP Network Analyzer:- - Make connectionS as per diagram between Analyzer, Transmission/Reflection test set and

75-120 Ω Transformer as shown in Fig. 6-5. - Measure/ Format key- Format- More-Log mag , - See yellow trace. - Start- Enter 51- Press X K1 function soft key, - Stop- enter 3072 Press cross K1 from soft key - Press cal- Select 1- port /3 -term from soft menu. - Connect Open connector to test port, - Press, ‘OPEN’ soft key, - Remove open connector and connect short connector, - Press ‘SHORT’ - Remove ‘SHORT’ and connect load 75Ω and Press ‘LOAD’-press ‘DONE’ - Remove load and connect E1 Rx under test through 75-120 Ω Transpower - Observe, trace on display for 51 KHz in the right corner see loss in dB - Tune all the frequencies given in table and note down the loss in dB - The Limits and Frequencies are given below:-

51.2 KHz to 102 KHz ≥ 12 dB 102 KHz to 2048 KHz ≥ 18 dB 2048 KHz to 3072 KHz ≥ 14 dB and the frequencies to be selected are 51 KHz, 100, 400, 600, 1000, 1500, 2500, 2600 and 3072 KHz. Return loss with W/G selective level :- Measuring set (PSM-137) with a W/G bridge RFZ-12

- Prepare a test set up as follows, Fig. no. 6-6. - Put ON - Press Blue button and set up - Select Ret loss/ Attenuation - Recall, Press red

Test Set Bridge

RT out R A

E1 Rx

Calibration with open/short connector

R A RF IN

Test 75120 port

Transpower

142

W/G PSM- 137

-17.5 3072 KHz

Rx 120 Tx 120

75 Ω 75 Ω

W/G RF 2- 12

Fig. 6-6

- Level display - 47.6, - Press left Ref key and right also, - Ref level goes to zero (Rx level) - Calibration is in built (Auto), - Press right key to select frequency, - Press 51.2 digits by digit key, - Connect E1, Rx to PCM-137 Rx (120 Ω), - Select frequencies as per table and note down the Rx levels, - Compare results with Specifications. 2. Measurement of clock frequency :- - Measure the Trans clock frequency , - Limit :- 2048 KHz ± 50 PPM (±102 Hz) i.e.2047898 to 2048102 Hz . 6-2.4 4 Check of Output pulse characteristics :- 1. With HP 54503 A Digitizing oscilloscope Pl. see Fig. 6-7.

E1 Rx

120

75 Ω

W

G

Tx

.75 .124 .135 .150 .600

Rx 75

120

143

- Make a test set up as below :-

Width

- Connect E1Rx to any one of four input ports, and select any o/o four ports. select 2 for 50 ohms. Press set up. Select frequency start and stop. - Press calibration, open, short, load to perform calibration. - Press marker, marker list. - Press set up and recall-1 for + pulse, Observe + pulse on display. Press 2 for – ve pulse. - In the bottom of oscilloscope read Pulse Amplitude and width, Rise and fall time of the pulse. - Note down the readings for corresponding frequency. - Calculate ratios for width and amplitude. - For Rise and Fall time move the cursor, and note reading. - The limits are as below: - Nominal

value Reading for example..

A. Pulse Amplitude + ve pulse 3.0 ± 0.3 V 2.96 - ve pulse 3.00 B. Pulse width + ve pulse 244 ± 24 ŋs 248 - ve pulse 252 C. Ratio of + ve & -ve Pulse amplitude 0.95 to 1.05 0.986 D. Ratio of +ve & -ve pulse width 0.95 to 1.05 0.984 E. Rise time + ve pulse ≤ 80 ŋs 28 - ve pulse 30 F. Fall Time + ve pulse ≤ 80 ŋs 30 - ve pulse 32

Test with Acterna E1 tester: - See Pulse mask in Fig. 6-8 and tester in Fig. 6-14

- There are six options, Menu 1 jitter function, E1 pulse shape and level, G826 performance. - Select E1 pulse shape level , Connect E1 Tx and Rx ( on Loop from MSC) - Press more two times set up- E1 pulse- S1- Wait.

75 Ω

1

75 Ω

120 Ω

WHEEL AMP

RT I/P FT A11

Pulse width RT FT

Fig. 6-7

144

- Select +ve or -ve polarity, Interface 120/ 75 Ω , - Run- Cal O.K – Results.

- Fig. 6-8 - Readings are as follows for example :- - Rise time 55 ŋs, Fall time 37 ŋs - Pulse width 253 ŋs, Overshoot 12 %, Under shoot 80% - Run test for +ve & -ve pulse , - Calculate the ratio as per mentioned table and its limit as - Ratio of pulse amplitude 0.95 to 1.05, - Ratio of pulse width 244 ± 24 ŋs 6-2.5 3. Jitter Test:- Input Jitter tolerance:- - Ask MSC to loop E1, Confirm loop by disconnection . - Connect E1 Tx and Rx to ANT 20 E or any DTA set with jitter modulator. With ANT-20 E: - - Make a test set up as below, - Open jitter generator and analyzer. - MTJ Set MTJ Setting- Select,(Maximum Tolerable Jitter ) - Scan frequencies by keyboard as 20 Hz,93 Hz,700 Hz and 100 KHz in a table, - Enter OK. - Jitter table Start after 2 to 3 minutes reading will start to be displayed, - select Mask run , - Take out print out of jitter table and mask which are shown in the next diagram no 6-9 on next page.

Upper mask

E1

Lower Mask

500 ŋs

145

146

147

6-2.7 8.Combine jitter and wander from tributary mapping and pointer adjustment (With Anritsu DTA set) The conditions are: -

1. Jitter ON, Wander OFF. 2. Wander ON, Jitter OFF. 3. HP1 + LP 20 Hz- 100 KHz. 4. HP2 + LP 18KHz- 100 KHz.

and under following conditions :- 5. a) Single pointer with opposite polarity separated by ≥ 10 S (n =1)

b) Regular pointer at every 0.75 s plus one double pointer (T3 = 2) with 2 ms spacing (43,44 in ANT-20E ) c) Regular pointers at every 0.75 s with missing pointer.

With Anritsu DTA set: -

Anritsu 1552 A

DDF Electrical

T T ROptical R

Fig. 6-11 - Make connections between DTA set, STM-1system and DDF as per above diagram. - Mapping for optical to electrical to be done in laptop. - Observe loop on DTA set- Select pointer sequence / filters and Jitter/ Wander ON - Note down the results as given below in the table for example: - - Results are for examples only with limits: -

F1-F4 (20 KHz-100 KHz) F3-F4 (18 KHz-100 KHz) Jitter ON Wander OFF a. 0.053 UI a. 0.032 UI b. 0.047 UI b. 0.031 UI c. 0.040 UI c. 0.047 UI Wander ON Jitter OFF a. 0.042 UI a. 0.031 UI b. 0.042 UI b. 0.031 UI c. 0.040 UI c. 0.046 UI Limit: - ≤ 0.4 UI ≤ 0.075 UI

Tx Rx

ECI

Tx RxSTM-1

148

6-2.8 If POI is offered on PCM cable then test PCM cable attenuation . Limit :- 6 dB at 1024 KHz. If connectivity between BSNL and vendors POP up is provided by copper cable with Modem then, ( See Fig. 6-12.)

- Chapter 4B measurement is not applicable. - Crone box termination and earthing to be checked. - Stability to be taken 24/ 96 as per onward media connectivity up to their MSC. - Safety measurements like GD tubes proved or not? - Attenuation test as Modem is provided , need not to take. - Return loss Measurement as described earlier. - Check of O/P pulse characteristics: - as described earlier. - O/P jitter, I/P jitter tolerance and Mask to be taken as mentioned earlier with print

outs. - End to End BER as usual to be carried out with loop from their MSC. - Jitter and wander not applicable. - Make one visit to vendor POP up and check their onward media.

POI A/T on Cu wire

Fig. 6-12

crone termination

-- - - - - -

-- - - - - -

- - - -- - - -

VSNL POP (Module)

Existing M/W on OFC System

Modem loop

MDF

E1

Loop Telecom 2048 Kbps

...… …

... …

MODEM

Line

Rx IN

Tx out

Loop- 4 TM 3900

Modem ON or remote supply

Cu Cable

0.9 mm

R B R B

R B R B

TAX/OCB

Rosette cord Loop Telecom loop-4 X DSL

Rosette ..Console ..

LED’s loop

149

150

151