Table Of Contents

Cable Specifications

Console and Auxiliary Port Cables and Pinouts

Identifying a Rollover Cable

Console Port Cables and Pinouts

Auxiliary Port Cables and Pinouts

Fast Ethernet Port Cables and Pinouts

Cisco 7120-4T1 and Cisco 7140-8T Cables and Pinouts

EIA/TIA-232 Connections

EIA/TIA-449 Connections

V.35 Connections

X.21 Connections

EIA-530 Connections

Cisco 7120-T3, Cisco 7120-E3, Cisco 7140-2T3, and Cisco 7140-2E3 Cables

Cisco 7120-AT3, Cisco 7140-2AT3, Cisco 7120-AE3, Cisco 7140-2AE3, Cisco 7120-SMI3, and Cisco 7140-2MM3 Cables

AT3 and AE3 Cables and Receptacles

MM3 and SMI3 Cables and Receptacles

Fiber-Optic Transmission Specifications

SONET Distance Limitations

Power Budget

Approximating the MM3 and SMI3 Port Power Margin

Multimode Power Budget Example with Sufficient Power for Transmission

Multimode Power Budget Example of Dispersion Limit

Single-Mode Transmission

SONET Single-Mode Power Budget Example

Using Statistics to Estimate the Power Budget

Cable Specifications

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This appendix provides the following cabling and pinout information for the Cisco 7100 series routers:

•Console and Auxiliary Port Cables and Pinouts

•Fast Ethernet Port Cables and Pinouts

•Cisco 7120-4T1 and Cisco 7140-8T Cables and Pinouts

•Cisco 7120-T3, Cisco 7120-E3, Cisco 7140-2T3, and Cisco 7140-2E3 Cables

•Cisco 7120-AT3, Cisco 7140-2AT3, Cisco 7120-AE3, Cisco 7140-2AE3, Cisco 7120-SMI3, and Cisco 7140-2MM3 Cables

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Note This appendix specifies pinouts only for the pins used. Pins not listed in the tables in this appendix are not connected.

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Console and Auxiliary Port Cables and Pinouts

The router arrives with a console and auxiliary cable kit, which contains the cable and adapters you need to connect a console (an ASCII terminal or PC running terminal emulation software) or modem to the router. The console and auxiliary cable kit includes:

•RJ-45-to-RJ-45 rollover cable

•RJ-45-to-DB-9 female data terminal equipment (DTE) adapter labeled TERMINAL

•RJ-45-to-DB-25 female DTE adapter labeled TERMINAL

•RJ-45-to-DB-25 male data communications equipment (DCE) adapter labeled MODEM

Identifying a Rollover Cable

You can identify a rollover cable by comparing the two modular ends of the cable. Holding the cables side-by-side, with the tab at the back, the wire connected to the pin on the outside of the left plug should be the same color as the wire connected to the pin on the outside of the right plug. (See Figure C-1.) If your cable was purchased from Cisco Systems, pin 1 will be white on one connector, and pin 8 will be white on the other connector (a rollover cable reverses pins 1 and 8, 2 and 7, 3 and 6, and 4 and 5).

Figure C-1 Identifying a Rollover Cable

Console Port Cables and Pinouts

Use the RJ-45-to-RJ-45 rollover cable and RJ-45-to-DB-9 female DTE adapter (labeled TERMINAL) to connect the console port to a PC running terminal emulation software. Table C-1 lists the signals and pinouts for the asynchronous serial console port, the RJ-45-to-RJ-45 rollover cable, and the RJ-45-to-DB-9 female DTE adapter (labeled TERMINAL).

Table C-1 Console Port Signaling and Cabling Using a DB-9 Adapter

Console Port (DTE)	RJ-45-to-RJ-45 Rollover Cable		RJ-45-to-DB-9 Terminal Adapter	Console Device
Signal	RJ-45 Pin	RJ-45 Pin	DB-9 Pin	Signal
RTS	11	8	8	CTS
DTR	2	7	6	DSR
TxD	3	6	2	RxD
GND	4	5	5	GND
GND	5	4	5	GND
RxD	6	3	3	TxD
DSR	7	2	4	DTR
CTS	81	1	7	RTS

1 Pin 1 is connected internally to pin 8.

Use the RJ-45-to-RJ-45 rollover cable and RJ-45-to-DB-25 female DTE adapter (labeled TERMINAL) to connect the console port to a terminal. Table C-2 lists the signals and pinouts for the asynchronous serial console port, the RJ-45-to-RJ-45 rollover cable, and the RJ-45-to-DB-25 female DTE adapter (labeled TERMINAL).

Table C-2 Console Port Signaling and Cabling Using a DB-25 Adapter

Console Port (DTE)1	RJ-45-to-RJ-45 Rollover Cable		RJ-45-to-DB-25 Terminal Adapter	Console Device
Signal	RJ-45 Pin	RJ-45 Pin	DB-25 Pin	Signal
RTS	12	8	5	CTS
DTR	2	7	6	DSR
TxD	3	6	3	RxD
GND	4	5	7	GND
GND	5	4	7	GND
RxD	6	3	2	TxD
DSR	7	2	20	DTR
CTS	81	1	4	RTS

1 You can use the same cabling to connect a console to the auxiliary port. 2 Pin 1 is connected internally to pin 8.

Auxiliary Port Cables and Pinouts

Use the RJ-45-to-RJ-45 rollover cable and RJ-45-to-DB-25 male DCE adapter (labeled MODEM) to connect the auxiliary port to a modem. Table C-3 lists the signals and pinouts for the asynchronous serial auxiliary port, the RJ-45-to-RJ-45 rollover cable, and the RJ-45-to-DB-25 male DCE adapter (labeled MODEM).

Table C-3 Auxiliary Port Signaling and Cabling Using a DB-25 Adapter 

AUX Port (DTE)	RJ-45-to-RJ-45 Rollover Cable		RJ-45-to-DB-25 Modem Adapter	Modem (DCE)
Signal	RJ-45 Pin	RJ-45 Pin	DB-25 Pin	Signal
RTS	1	8	4	RTS
DTR	2	7	20	DTR
TxD	3	6	3	TxD
GND	4	5	7	GND
GND	5	4	7	GND
RxD	6	3	2	RxD
DSR	7	2	8	DCD
CTS	8	1	5	CTS

Fast Ethernet Port Cables and Pinouts

The 10BaseT/100BaseTX Fast Ethernet ports support IEEE 802.3 and IEEE 802.3u specifications for 10-Mbps and 100-Mbps transmission over unshielded twisted-pair (UTP) cables. Each Fast Ethernet port on the router has an RJ-45 connector to attach to Category 3 or Category 5 UTP cables.

Cisco Systems does not supply Category 3 or Category 5 UTP RJ-45 cables; these cables are available commercially.

Use a Category 3 UTP crossover cable when connecting 10BaseT port to a hub or use a Category 3 UTP straight-through cable when connecting to an end station.

Use a Category 5 UTP crossover cable when connecting 100BaseTX to a hub or use a Category 5 UTP straight-through cable when connecting to an end station.

To determine the type of RJ-45 cable, examine the sequence of colored wires as follows:

•Straight-through—Colored wires are in the same sequence at both ends of the cable.

•Crossover—The first (far left) colored wire at one end of the cable is the third colored wire at the other end of the cable, and the second colored wire at one end of the cable is the sixth colored wire at the other end of the cable.

Table C-4 lists the 10BaseT pinouts and Table C-5 lists the 100BaseTX pinouts for the two Fast Ethernet ports.

Table C-4 10BaseT RJ-45 Connector Pinouts

RJ-45 Pin	Description
1	Tx+
2	Tx-
3	Rx+
6	Rx-

Table C-5 100BaseTX RJ-45 Connector Pinouts

RJ-45 Pin	Description
1	Tx+
2	Tx-
3	Rx+
6	Rx-

Figure C-2 shows the RJ-45 cable connectors.

Figure C-2 RJ-45 Plug and Receptacle

Cisco 7120-4T1 and Cisco 7140-8T Cables and Pinouts

The four T1 ports on the Cisco 7120-4T1 and the eight T1 ports on the Cisco 7140-8T and adapter cables allow a high density of interface ports, regardless of the size of the connectors typically used with each electrical interface type. All ports use an identical 60-pin D-shell receptacle that supports all interface types:

•EIA/TIA-232

•V.35

•EIA/TIA-449

•X.21

•EIA-530

Each port requires a serial adapter cable, which provides the interface between the high-density serial port and the standard connectors that are commonly used for each electrical interface type.

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Note The adapter cable determines the electrical interface type and mode of the port (DTE or DCE) to which it is connected.

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The network end of the cable is an industry-standard connector for the type of electrical interface that the cable supports. For most interface types, the adapter cable for DTE mode uses a plug at the network end, and the cable for DCE mode uses a receptacle at the network end. Exceptions are V.35 adapter cables, which are available with either a V.35 plug or a receptacle for either mode, and the EIA-530 adapter cable, which is available only in DTE mode with a DB-25 plug at the network end. The mode is labeled on the molded plastic connector shell at the ends of all cables except V.35 (which uses the standard Winchester block-type connector instead of a molded plastic D shell).

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Caution Serial interface cables must be attached correctly, or damage to the cable plug will result. Attempting to force a cable plug on the 60-pin receptacle can damage the plug. (See Figure C-3.)

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Figure C-3 Correct Serial Cable Orientation

Table C-6 lists the available interface cable options (and product numbers) for the mode and network-end connectors.

Table C-6 Serial Cable Product Numbers

Interface Type	Description	Product Number
EIA/TIA-232	DTE mode with a DB-25 plug	CAB-232MT=
	DCE mode with a DB-25 receptacle	CAB-232FC=
EIA/TIA-449	DTE mode with a 37-pin D-shell plug	CAB-449MT=
	DCE mode with a 37-pin D-shell receptacle	CAB-449C=
V.35	DTE mode or DCE mode with a 34-pin Winchester-type V.35 plug	CAB-V35MT= or CAB-V35MC=
	DTE mode or DCE mode with a 34-pin Winchester-type V.35 receptacle	CAB-V35FT= or CAB-V35FC=
	Male DB-60 plug on the router end and a male DB-34 shielded plug on the network end	CAB-V35MTS=
X.21	DTE mode with a DB-15 plug	CAB-X21MT=
	DCE mode with a DB-25 receptacle	CAB-X21FC=
EIA-530	DTE mode with a DB-25 plug	CAB-530MT=

Figure C-4 shows the supported serial cables.

Figure C-4 T1 Serial Cables

Metric (M3) thumbscrews are included with each cable to allow connections to devices that use metric hardware. Because the T1 ports use a special, high-density port that requires special adapter cables for each electrical interface type, we recommend that you obtain serial interface cables from the factory.

Serial signals can travel a limited distance at any given bit rate; generally, the slower the baud rate, the greater the distance. All serial signals are subject to distance limits beyond which a signal degrades significantly or is completely lost.

Table C-7 lists the recommended (standard) maximum speeds and distances for each serial interface type. The recommended maximum rate for V.35 is 2.048 Mbps.

Table C-7 Recommended (Standard) Maximum Speeds and Distances for Serial Interfaces 

	EIA/TIA-232 Distances		EIA/TIA-449, X.21, V.35, EIA-530 Distances
Rate (bps)	Feet	Meters	Feet	Meters
2400	200	60	4,100	1,250
4800	100	30	2,050	625
9600	50	15	1,025	312
19200	25	7.6	513	156
38400	12	3.7	256	78
56000	8.6	2.6	102	31
1544000 (T1)	-	-	50	15

Balanced drivers allow EIA/TIA-449 signals to travel greater distances than EIA/TIA-232 signals. The recommended distance limits for EIA/TIA-449 shown in Table C-7 are also valid for V.35, X.21, and EIA-530. EIA/TIA-449 and EIA-530 support 2.048-Mbps rates, and V.35 supports 2.048-Mbps rates without any problems; we do not recommend exceeding published specifications for transmission speed versus distance. Do so at your own risk.

EIA/TIA-232 Connections

The router end of all EIA/TIA-232 adapter cables is a high-density 60-pin plug. The network end of the adapter cable is a standard 25-pin D-shell connector (known as a DB-25) that is commonly used for EIA/TIA-232 connections. Figure C-5 shows the connectors at the network end of the adapter cable.

Do not use the Cisco Systems-provided EIA/TIA-232 adapter cable product number CAB-232MT= to connect a T1 interface that is configured for DTE mode directly to an NEC - NEXTSTAR 1E model C4969 MD/SAC unit interface that is configured for DCE mode. Doing so will keep transmit and receive data signals from being properly exchanged between the two interfaces.

Instead, you must connect an additional, intermediate adapter cable—with standard EIA/TIA-232 DB-25 connectors at both ends—from the network end of product number CAB-232MT= to the standard EIA/TIA-232 DB-25 connector (the DCE interface) on the NEC - NEXTSTAR 1E model C4969 MD/SAC unit. Cisco Systems does not provide this additional cable; however, its signals and pin assignments are listed in Table C-8.

You can use the Cisco Systems-provided EIA/TIA-232 adapter cable product number CAB-232FC= to connect a T1 interface that is configured for DCE mode directly to an NEC - NEXTSTAR 1E model C4969 MD/SAC unit interface that is configured for DTE mode. This cable's pin assignments are listed in Table C-9.

Figure C-5 EIA/TIA-232 Adapter Cable Connectors

Table C-8 EIA/TIA-232 Adapter Cable Signals (DTE) 

DTE Cable (CAB-232MT=)
Router End, HD1 60-Position Plug				Network End, DB-25 Plug
Signal	Pin		Pin	Signal
Shield ground	46	-	1	Shield ground
TxD/RxD	41	—>	2	TxD
RxD/TxD	36	<—	3	RxD
RTS/CTS	42	—>	4	RTS
CTS/RTS	35	<—	5	CTS
DSR/DTR	34	<—	6	DSR
Circuit ground	45	-	7	Circuit ground
DCD/LL	33	<—	8	DCD
TxC/NIL	37	<—	15	TxC
RxC/TxCE	38	<—	17	RxC
LL/DCD	44	—>	18	LTST
DTR/DSR	43	—>	20	DTR
TxCE/TxC	39	—>	24	TxCE
Mode 0 Ground Mode_DCE	50 51 52	-	-	Shorting group

1 HD = high-density.

Table C-9 EIA/TIA-232 Adapter Cable Signals (DCE) 

DCE Cable (CAB-232FC=)
Router End, HD1 60-Position Plug				Network End, DB-25 Receptacle
Signal	Pin		Pin	Signal
Shield ground	46	-	1	Shield ground
RxD/TxD	36	<—	2	TxD
TxD/RxD	41	—>	3	RxD
CTS/RTS	35	<—	4	RTS
RTS/CTS	42	—>	5	CTS
DTR/DSR	43	—>	6	DSR
Circuit ground	45	-	7	Circuit ground
LL/DCD	44	—>	8	DCD
TxCE/TxC	39	—>	15	TxC
NIL/RxC	40	—>	17	RxC
DCD/LL	33	<—	18	LTST
DSR/DTR	34	<—	20	DTR
RxC/TxCE	38	<—	24	TxCE
Mode 0 Ground	50 51	-	-	Shorting group

1 HD = high-density.

EIA/TIA-449 Connections

The router end of all EIA/TIA-449 adapter cables is a high-density 60-pin plug. The network end of the adapter cable provides a standard 37-pin D-shell connector, which is commonly used for EIA/TIA-449 connections. Figure C-6 shows the connectors at the network end of the adapter cable. EIA/TIA-449 cables are available as either DTE (DB-37 plug) or DCE (DB-37 receptacle). See Table C-10 and Table C-11 for pinouts.

Figure C-6 EIA/TIA-449 Adapter Cable Connectors

Table C-10 EIA/TIA-449 Adapter Cable Signals (DTE) 

DTE Cable (CAB-449MT=)
Router End, HD1 60-Position Plug				Network End, DB-37 Plug
Signal	Pin		Pin	Signal
Shield ground	46	-	1	Shield ground
TxD/RxD+	11	—>	4	SD+
TxD/RxD-	12	—>	22	SD-
TxC/RxC+	24	<—	5	ST+
TxC/RxC-	23	<—	23	ST-
RxD/TxD+	28	<—	6	RD+
RxD/TxD-	27	<—	24	RD-
RTS/CTS+	9	—>	7	RS+
RTS/CTS-	10	—>	25	RS-
RxC/TxCE+	26	<—	8	RT+
RxC/TxCE-	25	<—	26	RT-
CTS/RTS+	1	<—	9	CS+
CTS/RTS-	2	<—	27	CS-
LL/DCD	44	—>	10	LL
Circuit ground	45	-	37	SC
DSR/DTR+	3	<—	11	ON+
DSR/DTR-	4	<—	29	ON-
DTR/DSR+	7	—>	12	TR+
DTR/DSR-	8	—>	30	TR-
DCD/DCD+	5	<—	13	RR+
DCD/DCD-	6	<—	31	RR-
TxCE/TxC+	13	—>	17	TT+
TxCE/TxC-	14	—>	35	TT-
Circuit ground	15	-	19	SG
Circuit ground	16	-	20	RC
Mode 1 Ground	49 48	-	-	Shorting group
Ground Mode_DCE	51 52	-	-	Shorting group

1 HD = high-density.

Table C-11 EIA/TIA-449 Adapter Cable Signals (DCE) 

DCE Cable (CAB-449C=)
Router End, HD1 60-Position Plug				Network End, DB-37 Receptacle
Signal	Pin		Pin	Signal
Shield ground	46	-	1	Shield ground
RxD/TxD+	28	<—	4	SD+
RxD/TxD-	27	<—	22	SD-
TxCE/TxC+	13	—>	5	ST+
TxCE/TxC-	14	—>	23	ST-
TxD/RxD+	11	—>	6	RD+
TxD/RxD-	12	—>	24	RD-
CTS/RTS+	1	<—	7	RS+
CTS/RTS-	2	<—	25	RS-
TxC/RxC+	24	—>	8	RT+
TxC/RxC-	23	—>	26	RT-
RTS/CTS+	9	—>	9	CS+
RTS/CTS-	10	—>	27	CS-
NIL/LL	29	—>	10	LL
Circuit ground	30	-	37	SC
DTR/DSR+	7	—>	11	ON+
DTR/DSR-	8	—>	29	ON-
DSR/DTR+	3	<—	12	TR+
DSR/DTR-	4	<—	30	TR-
DCD/DCD+	5	—>	13	RR+
DCD/DCD-	6	—>	31	RR-
RxC/TxCE+	26	<—	17	TT+
RxC/TxCE-	25	<—	35	TT-
Circuit ground	15	-	19	SG
Circuit ground	16	-	20	RC
Mode 1 Ground	49 48	-	-	Shorting group

1 HD = high-density.

V.35 Connections

The router end of all V.35 adapter cables is a high-density 60-pin plug. The network end of the adapter cable provides a standard 34-pin Winchester-type connector commonly used for V.35 connections. Figure C-7 shows the connectors at the network end of the V.35 adapter cable. V.35 cables are available with a standard V.35 plug for DTE mode (CAB-V35MT=) or a V.35 receptacle for DCE mode (CAB-V35FC=). See Table C-12 and Table C-13 for pinouts.

Figure C-7 V.35 Adapter Cable Connectors

Also available, but not shown in Figure C-7, are CAB-V35MC=, a V.35 cable with a plug on the network end for DCE mode, and CAB-V35FT=, a V.35 cable with a receptacle on the network end for DTE mode. These cables are used for connecting V.35-equipped systems back to back.

Table C-12 V.35 Adapter Cable Signals (DTE) 

DTE Cable (CAB-V35FT= or CAB-V35MT=)
Router End, HD1 60-Position Plug				Network End, 34-Position Plug
Signal	Pin		Pin	Signal
Shield ground	46	-	A	Frame ground
Circuit ground	45	-	B	Circuit ground
RTS/CTS	42	—>	C	RTS
CTS/RTS	35	<—	D	CTS
DSR/DTR	34	<—	E	DSR
DCD/LL	33	<—	F	RLSD
DTR/DSR	43	—>	H	DTR
LL/DCD	44	—>	K	LT
TxD/RxD+	18	—>	P	SD+
TxD/RxD-	17	—>	S	SD-
RxD/TxD+	28	<—	R	RD+
RxD/TxD-	27	<—	T	RD-
TxCE/TxC+	20	—>	U	SCTE+
TxCE/TxC-	19	—>	W	SCTE-
RxC/TxCE+	26	<—	V	SCR+
RxC/TxCE-	25	<—	X	SCR-
TxC/RxC+	24	<—	Y	SCT+
TxC/RxC-	23	<—	AA	SCT-
Mode 1 Ground	49 48	-	-	Shorting group
Mode 0 Ground Mode_DCE	50 51 52	-	-	Shorting group
TxC/NIL RxC/TxCE RxC/TxD Ground	53 54 55 56	-	-	Shorting group

1 HD = high-density.

Table C-13 V.35 Adapter Cable Signals (DCE) 

DCE Cable (CAB-V35FC= or CAB-V35MC=)
Router End, HD1 60-Position Plug				Network End, 34-Position Receptacle
Signal	Pin		Pin	Signal
Shield ground	46	-	A	Frame ground
Circuit ground	45	-	B	Circuit ground
CTS/RTS	35	<—	C	RTS
RTS/CTS	42	—>	D	CTS
DTR/DSR	43	—>	E	DSR
LL/DCD	44	—>	F	RLSD
DSR/DTR	34	<—	H	DTR
DCD/LL	33	<—	K	LT
RxD/TxD+	28	<—	P	SD+
RxD/TxD-	27	<—	S	SD-
TxD/RxD+	18	—>	R	RD+
TxD/RxD-	17	—>	T	RD-
RxC/TxCE+	26	<—	U	SCTE+
RxC/TxCE-	25	<—	W	SCTE-
NIL/RxC+	22	—>	V	SCR+
NIL/RxC-	21	—>	X	SCR-
TxCE/TxC+	20	—>	Y	SCT+
TxCE/TxC-	19	—>	AA	SCT-
Mode 1 Ground	49 48	-	-	Shorting group
Mode 0 Ground	50 51	-	-	Shorting group
TxC/NIL RxC/TxCE RxC/TxD Ground	53 54 55 56	-	-	Shorting group

1 HD = high-density.

X.21 Connections

The router end of all X.21 adapter cables is a high-density 60-pin plug. The network end of the adapter cable is a standard DB-15 connector. Figure C-8 shows the connectors at the network end of the X.21 adapter cable. X.21 cables are available as either DTE (DB-15 plug) or DCE (DB-15 receptacle). See Table C-14 and Table C-15 for pinouts.

Figure C-8 X.21 Adapter Cable Connectors

Table C-14 X.21 Adapter Cable Signals (DTE)

DTE Cable (CAB-X21MT=)
Router End, HD1 60-Position Plug				Network End, DB-15 Plug
Signal	Pin		Pin	Signal
Shield ground	46	-	1	Shield ground
TxD/RxD+	11	—>	2	Transmit+
TxD/RxD-	12	—>	9	Transmit-
RTS/CTS+	9	—>	3	Control+
RTS/CTS -	10	—>	10	Control-
RxD/TxD+	28	<—	4	Receive+
RxD/TxD-	27	<—	11	Receive-
CTS/RTS+	1	<—	5	Indication+
CTS/RTS -	2	<—	12	Indication-
RxC/TxCE+	26	<—	6	Timing+
RxC/TxCE-	25	<—	13	Timing-
Circuit ground	15	-	8	Circuit ground
Ground Mode_2	48 47	-	-	Shorting group
Ground Mode_DCE	51 52	-	-	Shorting group

1 HD = high-density.

Table C-15 X.21 Adapter Cable Signals (DCE) 

DCE Cable (CAB-X21FC=)
Router End, HD1 60-Position Plug				Network End, DB-15 Receptacle
Signal	Pin		Pin	Signal
Shield ground	46	-	1	Shield ground
RxD/TxD+	11	—>	2	Transmit+
RxD/TxD-	12	—>	9	Transmit-
CTS/RTS+	9	—>	3	Control+
CTS/RTS -	10	—>	10	Control-
TxD/RxD+	28	<—	4	Receive+
TxD/RxD-	27	<—	11	Receive-
RTS/CTS+	1	<—	5	Indication+
RTS/CTS-	2	<—	12	Indication-
TxC/RxC+	26	<—	6	Timing+
TxC/RxC -	25	<—	13	Timing-
Circuit ground	15	-	8	Circuit ground
Ground Mode_2	48 47	-	-	Shorting group
Ground Mode_DCE	51 52	-	-	-

1 HD = high-density.

EIA-530 Connections

The EIA-530 adapter cable is available in DTE mode only. The router end of the EIA-530 adapter cable is a high-density 60-pin plug. The network end of the adapter cable is a standard DB-25 plug commonly used for EIA/TIA-232 connections. Figure C-9 shows the DB-25 connector at the network end of the adapter cable.

Figure C-9 EIA-530 Adapter Cable Connector

Table C-16 EIA-530 DTE Adapter Cable Signals (CAB-530MT=)

Router End, HD1 60-Position Plug				Network End, DB-25 Plug
Signal	Pin		Pin	Signal
Shield ground	46	-	1	Shield ground
TxD/RxD+	11	—>	2	TxD+
TxD/RxD-	12	—>	14	TxD-
RxD/TxD+	28	<—	3	RxD+
RxD/TxD-	27	<—	16	RxC-
RTS/CTS+	9	—>	4	RTS+
RTS/CTS-	10	—>	19	RTS-
CTS/RTS+	1	<—	5	CTS+
CTS/RTS-	2	<—	13	CTS-
DSR/DTR+	3	<—	6	DSR+
DSR/DTR-	4	<—	22	DSR-
DCD/DCD+	5	<—	8	DCD+
DCD/DCD-	6	<—	10	DCD-
TxC/RxC+	24	<—	15	TxC+
TxC/RxC-	23	<—	12	TxC-
RxC/TxCE+	26	<—	17	RxC+
RxC/TxCE-	25	<—	9	RxC-
LL/DCD	44	—>	18	LL
Circuit ground	45	-	7	Circuit ground
DTR/DSR+	7	—>	20	DTR+
DTR/DSR-	8	—>	23	DTR-
TxCE/TxC+	13	—>	24	TxCE+
TxCE/TxC-	14	—>	11	TxCE-
Mode_1 Ground Mode_2	49 48 47	-	-	Shorting group
Ground Mode_DCE	51 52	-	-	Shorting group

1 HD = high-density.

Cisco 7120-T3, Cisco 7120-E3, Cisco 7140-2T3, and Cisco 7140-2E3 Cables

The T3 or E3 serial interface cable on the Cisco 7120 and Cisco 7140 series, which is a 75-ohm coaxial cable, is used to connect your router to a T3 or E3 serial network. Serial cables conform to EIA/TIA-612 and EIA/TIA-613 specifications. The serial ports are considered to be DTE devices.

The T3 or E3 serial port has two connectors (receive and transmit) where you connect the Cisco 75-ohm coaxial cable. The 75-ohm coaxial cable (Cisco product number CAB-ATM-DS3/E3), is available only from Cisco Systems; it is not available from outside commercial cable vendors.

Figure C-10 shows the Cisco 75-ohm coaxial cable, which is available in 10-foot (3.05-meter) lengths only. The typical maximum distance between stations for T3 or E3 transmissions is 1300 feet (396 meters).

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Note For E3 (75-ohm) connections, you must have ferrite beads on the 75-ohm coaxial cable and electromagnetic interference (EMI) decoupling clips on the receiver end of the cable (see Figure C-10) if compliance with European certification standards for emission control is required (EN55022/CISPR22 Class B for radiated emission levels).

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Figure C-10 T3 and E3 Serial Port Adapter Cables

The T3 and E3 ports support several types of integrated data service units (DSUs). Table C-17 lists the features supported.

Table C-17 Feature Compatibilities of T3 and E3 Serial Port DSUs 

Device	Full Rate	Scrambling	Subrate	MDL1
T3 DSU
DL3100	Yes	Yes	Yes	No
Kentrox	Yes	Yes2	Yes2	No
Larscom	Yes	Yes	Yes	No
E3 DSU
DL3100E	Yes	No3	Yes3	No
Kentrox	Yes	Yes2	Yes2	No

1 MDL = Maintenance Digital Link. 2 T3 and E3 serial ports support either scrambling or Kentrox subrate, not both at the same time. 3 DL3100E does not support scrambling. However, the E3 serial port can turn on scrambling in DSU mode 0 for connecting to another E3 serial port. The E3 serial port supports either scrambling (in mode 0) or DL3100E subrate, not both at the same time.

Cisco 7120-AT3, Cisco 7140-2AT3, Cisco 7120-AE3, Cisco 7140-2AE3, Cisco 7120-SMI3, and Cisco 7140-2MM3 Cables

The AT3, AE3, MM3 (OC-3c/STM-1 multimode), and SMI3 (OC-3c/STM-1 single-mode intermediate reach) interfaces in Cisco 7120 series and Cisco 7140 series routers are full duplex. You must use the appropriate ATM interface cable to connect the interface with an external ATM network. These interfaces are considered DTE devices.

Table C-18 summarizes the interface types, connectors, and cables.

Table C-18 AT3, AE3, MM3, and SMI3 Connector Types and Cables 

Interface	Rate (Mbps)	Connector Type	Cable Type	ITU-T G.957 Standard	Bellcore GR-253 Standard	Wave- length	Maximum Distance
AT3	44.736	BNC	Coaxial	-	-	-	450 ft (137.2 m)
AE3	34.368	BNC	Coaxial	-	-	-	1250 ft (381 m)
MM3	155.52	SC	62.5/125 microns multimode	Intra-office STM-1 I-1	Short reach OC3	1310 nm	1.2 mi (2 km)
SMI3	155.52	SC	9 microns single mode	Short-haul STM-1 S-1.1	Intermediate reach OC3	1310 nm	9.3 mi (15 km)

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Note The ATM port is considered a DTE device.

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AT3 and AE3 Cables and Receptacles

The AT3 and AE3 interfaces provide an interface to ATM switching fabrics for the bidirectional transmission and reception of data at rates of up to 45 Mbps (for T3) and 34 Mbps (for E3).

The AT3 and AE3 interfaces use a 75-ohm coaxial interface cable to connect your router to an ATM T3 or E3 network. The AT3 and AE3 cables (see Figure C-11) conform to EIA/TIA-612 and EIA/TIA-613 specifications. The AT3 and AE3 ports are considered DTE devices.

Figure C-11 AT3 and AE3 Cables

AT3 or AE3 ports consist of two connectors, transmit and receive. The 75-ohm coaxial cable (Cisco product number CAB-ATM-DS3/E3) is available only from Cisco Systems; it is not available from outside commercial cable vendors.

The Cisco 75-ohm coaxial cable is available only in 10-foot (3.05-meter) lengths. The typical maximum distance between stations for T3 and E3 transmissions is 1300 feet (396 meters).

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Note To ensure compliance with EMI and European certification standards for emission control (EN55022/CISPR22 Class B for radiated emission levels), the transmit and receive cables should be tied together along their entire length, and ferrite beads should be installed on each cable near the transmit and receive connectors.

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MM3 and SMI3 Cables and Receptacles

The MM3 (OC-3c/STM-1 multimode) and SMI3 (OC-3c/STM-1 single-mode intermediate reach) interfaces provides an interface to ATM switching fabrics for transmitting and receiving data at rates of up to 155 Mbps bidirectionally. The MME and SMI3 interfaces connect to SONET/SDH, 155-Mbps multimode or single-mode optical fiber.

For SONET/SDH multimode and SONET/SDH single-mode connections, use one duplex SC connector (see Figure C-12) or two simplex SC connectors (see Figure C-13). The simplex and duplex SC connectors are shipped with removable dust covers on each connector.

Figure C-12 Duplex SC Connector

Figure C-13 Simplex SC Connector

An OC-3 ATM interface cable, which is used to connect your router to an external DSU (an ATM network), is available for use with the MM3 and SMI3 interfaces. Cables can be obtained from an outside cable vendor.

Single-mode and multimode cables should perform to the specifications listed in Table C-19.

Table C-19 Fiber-Optic Cable Specifications  

Standard	Maximum Path Length	Cabling
ISO/IEC 9314-3	1.2 miles (2 km) all cables in a connection, end to end	62.5-micron core with an optical loss of 0-9 dB, or 50-micron core with an optical loss of 7 dB
IEC 793-2	24.8 mi (40 km) for SML1 and 9.3 mi (15 km) for SMI2	9-micron core
ANSI/TIA/EIA-492CAAA	24.8 mi (40 km) for SML and 9.3 mi (15 km) for SMI	9-micron core

1 SML = single-mode long reach. 2 SMI = single-mode intermediate reach.

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Note A single fiber link should not mix 62.5- and 50-micron cable.

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Fiber-Optic Transmission Specifications

The following sections describe the SONET specifications for fiber-optic transmissions, define the power budget, and help you approximate the power margin for multimode and single-mode transmissions.

For more information on determining attenuation and power budget, see the following publications:

•T1E1.2/92-020R2 ANSI, the Draft American National Standard for Telecommunications entitled Broadband ISDN Customer Installation Interfaces: Physical Layer Specification.

•Power Margin Analysis, AT&T Technical Note, TN89-004LWP, May 1989

SONET Distance Limitations

The SONET specification for fiber-optic transmission defines two types of fiber: single mode and multimode. Modes can be thought of as bundles of light rays entering the fiber at a particular angle. Single-mode fiber allows only one mode of light to propagate through the fiber, whereas multimode fiber allows multiple modes of light to propagate through the fiber. Because multiple modes of light propagating through the fiber travel different distances depending on the entry angles, causing them to arrive at the destination at different times (a phenomenon called modal dispersion), single-mode fiber is capable of higher bandwidth and greater cable run distances than multimode fiber.

The typical maximum distances for single-mode and multimode transmissions, as defined by SONET, are in Table C-20. If the distance between two connected stations is greater than this maximum distance, significant signal loss can result, making transmission unreliable.

Table C-20 SONET Maximum Fiber-Optic Transmission Distances  

Transceiver Type	Maximum Distance between Stations1
Single-mode long reach (SML)	Up to 24.8 miles (40 kilometers)
Single-mode intermediate reach (SMI)	Up to 9.3 miles (15 kilometers)
Multimode (MM)	Up to 1.2 miles (2 kilometers)

1 Table C-20 gives typical results. Use the power budget calculations described in the following sections to determine the actual distances.

Power Budget

To design an efficient optical data link, evaluate the power budget. The power budget is the amount of light available to overcome attenuation in the optical link and to exceed the minimum power that the receiver requires to operate within its specifications. Proper operation of an optical data link depends on modulated light reaching the receiver with enough power to be correctly demodulated.

Attenuation, caused by the passive media components (cables, cable splices, and connectors), is common to both multimode and single-mode transmission.

The following variables reduce the power of the signal (light) transmitted to the receiver in multimode transmission:

•Chromatic dispersion—Spreading of the signal in time because of the different speeds of light wavelengths

•Modal dispersion—Spreading of the signal in time because of the different propagation modes in the fiber

Attenuation is significantly lower for optical fiber than for other media. For multimode transmission, chromatic and modal dispersion reduce the available power of the system by the combined dispersion penalty (dB). The power lost over the data link is the sum of the component, dispersion, and modal losses.

Table C-21 lists the factors of attenuation and dispersion for typical fiber-optic cable.

Table C-21 Typical Fiber-Optic Link Attenuation and Dispersion Limits  

Limits	Single-mode	Multimode
Attenuation	0.5 dB/km	1.0 dB/km
Dispersion	No limit	500 MHz/km1

1 The product of bandwidth and distance must be less than 500 MHz/km.

Approximating the MM3 and SMI3 Port Power Margin

The LED used for a multimode transmission light source creates multiple propagation paths of light, each with a different path length and time requirement to cross the optical fiber, causing signal dispersion (smear). Higher-order mode loss (HOL) results from light from the LED entering the fiber and being radiated into the fiber cladding. A worst-case estimate of power margin (PM) for multimode transmissions assumes minimum transmitter power (PT), maximum link loss (LL), and minimum receiver sensitivity (PR). The worst-case analysis provides a margin of error; not all of the parts of an actual system will operate at the worst-case levels.

The power budget (PB) is the maximum possible amount of power transmitted. The following equation lists the calculation of the power budget:

PB = P_T - P_R

PB = -20 dBm - (-30 dBm)

PB = 10 dB

The power margin calculation is derived from the power budget minus the link loss, as follows:

PM = PB - LL

If the power margin is positive, the link will work.

Table C-22 lists the factors that contribute to link loss and the estimate of the link loss value attributable to those factors.

Table C-22 Link Loss Factors and Values 

Link Loss Factor	Estimate of Link Loss Value
Higher-order mode losses	0.5 dB
Clock recovery module	1 dB
Modal and chromatic dispersion	Dependent on fiber and wavelength used
Connector	0.5 dB
Splice	0.5 dB
Fiber attenuation	1 dB/km

After calculating the power budget minus the data link loss, the result should be greater than zero. Circuits whose results are less than zero may have insufficient power to operate the receiver.

The SONET specification requires that the signal must meet the worst-case parameters listed in Table C-23.

Table C-23 MM3 and SMI3 Port SONET Signal Requirements

Variable	Single Mode (SML)	Single Mode (SMI)	Multimode
PT	-5 dBm	-15 dBm	-20 dBm
PR	-34 dBm	-31 dBm	-30 dBm
PB	29 dBm	16 dB	10 dB

Multimode Power Budget Example with Sufficient Power for Transmission

The following is an example multimode power budget calculated based on the following variables:

•Length of multimode link = 3 kilometers (km)

•Four connectors

•Three splices

•Higher-order mode loss (HOL)

•Clock recovery module (CRM)

Estimate the power budget as follows:

PB = 10 dB - 3 km (1.0 dB/km) - 4 (0.5 dB) - 3 (0.5 dB) - 0.5 dB (HOL) - 1 dB (CRM)

PB = 10 dB - 3 dB - 2 dB - 1.5 dB - 0.5 dB - 1 dB

PB = 2 dB

The positive value of 2 dB indicates that this link would have sufficient power for transmission.

Multimode Power Budget Example of Dispersion Limit

Following is an example with the same parameters as the previous example, but with a multimode link distance of 4 km:

PB = 10 dB - 4 km (1.0 dB/km) - 4 (0.5 dB) - 3 (0.5 dB) - 0.5 dB (HOL) - 1 dB (CRM)

PB = 10 dB - 4 dB - 2 dB - 1.5 dB - 0.5 dB - 1 dB

PB = 1 dB

The value of 1 dB indicates that this link would have sufficient power for transmission. But, due to the dispersion limit on the link (4 km x 155.52 MHz > 500 MHz/km), this link would not work with multimode fiber. In this case, single-mode fiber would be the better choice.

Single-Mode Transmission

The single-mode signal source is an injection laser diode. Single-mode transmission is useful for longer distances, because there is a single transmission path within the fiber and smear does not occur. In addition, chromatic dispersion is also reduced because laser light is essentially monochromatic.

The receiver for single-mode intermediate reach (SMI) cannot be overloaded by the SMI transmitter and does not require a minimum fiber cable length or loss. The maximum receive power for single-mode long reach (SML) is -10 dBm, and the maximum transmit power is 0 dBm. The SML receiver can, therefore, be overloaded when short lengths of fiber are used. Overloading the receiver will not damage the receiver but can cause unreliable operation. To prevent overloading an SML receiver connected with short fiber links, insert a minimum 10-dB attenuator on the link between any single-mode long-reach transmitter and the receiver.

SONET Single-Mode Power Budget Example

The following example of a single-mode power budget assumes 2 buildings, 8 kilometers apart, connected through a patch panel in an intervening building with a total of 12 connectors.

•Length of single-mode link = 8 km

•12 connectors

Estimate the power budget as follows:

PM = PB - LL

PM = 16 dB - 8 km (0.5 dB/km) - 12 (0.5 dB)

PM = 16 dB - 4 dB - 6 dB

PM = 6 dB

The value of 6 dB indicates that this link would have sufficient power for transmission and is not in excess of the maximum receiver input power.

Using Statistics to Estimate the Power Budget

Statistical models more accurately determine the power budget than the worst-case method. Determining the link loss with statistical methods requires accurate knowledge of variations in the data link components. Statistical power budget analysis is beyond the scope of this document. For further information, refer to UNI Forum specifications, ITU-T standards, and your equipment specifications.