Introduction to Passive Optical Network

A passive optical network (PON) or Gigabit Passive Optical Network (GPON) is a point-to-multipoint (P2MP) network that uses a combination of active transmission equipments and passive cable components to provide network connectivity to end user's devices. This network is suitable for building access networks such as fiber-to-the-home (FTTH), or fiber-to-the-office (FTTO), or fiber-to-the-company (FTTC) for providing internet access by running fiber optic cable directly from an internet service provider to a user's home or business. The PON technology is based on the ITU-T G.984 standard.

PON transmits Ethernet, Asynchronous Transfer Mode (ATM), and Time Division Multiplexing (TDM) traffic. It consists of mainly two active transmission equipments, Optical Line Terminal (OLT) and Optical Network Terminal (ONT). One of the main characteristics of PON is the use of passive optical splitters in the fiber distribution network, enabling a single feeding fiber from the service provider’s central office to serve multiple homes and small businesses.

The network path between the terminals is known as Optical Device Network (ODN), which comprises passive optical components, such as optical fibers and passive optical splitters. The ODN provides optical channels that interconnect the OLT to the ONTs. The optical fiber cables cover a distance of 20km to 30km.

A single optical fiber from the OLT connects to a passive optical splitter that is located near an end user's premises. The optical splitter divides optical power into n separate paths to end user. The number of optical paths can vary from 2 to 128. From the optical splitter, a single-mode fiber strand is connected to each end user's devices. Data is broadcast in the downstream direction and transmitted in the TDMA mode based on timeslots in the upstream direction.

The data, voice, and video signals of an end-user devices are sent to ONTs. The signals are converted into GPON Encapsulation Method (GEM) frames and then transmitted over optical fibers to the OLT using the PON uplink ports on the ONTs. On the OLT the GEM frames are converted into Ethernet packets and are forwarded to the upper-layer IP network using the uplink port on the OLT.

For more information, see the following sections:

Cisco Catalyst PON Series OLT Overview

The Cisco Catalyst PON Series OLT is an aggregation device that is located at a service provider's central office of the PON network. The main functions of a Cisco Catalyst PON Series OLT are traffic scheduling, buffer control, and bandwidth allocation. The Cisco Catalyst PON Series OLT manages the network traffic that is in the form of video, data, and voice signals in a PON network, and sends them downstream to the Cisco Catalyst PON Series ONTs on the network. The Cisco Catalyst PON Series OLT also receives the signals from the Cisco Catalyst PON Series ONTs located at an end user's premises and sends them to their destination over the internet.

A Cisco Catalyst PON Series OLT can support up to 128 Cisco Catalyst PON Series ONTs per port. A Cisco Catalyst PON Series OLT provides 8/16xPON ports, 4xG combo ports and 2x10G small form-factor pluggable (SFP+) ports for uplink. A Cisco Catalyst PON Series OLT carries abundant services and flexible network mode over one optical network, and is especially suitable for networks such as enterprise LAN, video application, and high-speed internet.

Cisco Catalyst PON Series OLT Models

The following table lists the Cisco Catalyst PON Series OLT models and their description.

Table 1. Cisco Catalyst PON Series OLT Models and Description
Model	Description
CGP-OLT-8T	Cisco Catalyst PON Series OLT with 8xPON port, 4x1 G combo port, and 2x10 G SFP+ module uplink slot.
CGP-OLT-16T	Cisco Catalyst PON Series OLT with 16xPON port, 4x1 G combo port, and 2x10 G SFP+ module uplink slot.

Front Panel

This section describes the front-panel components of Cisco Catalyst PON Series OLT.


1	PON ports	7	System LEDs
2	1 G combo ports	8	Auxiliary port
3	10 G SFP+ ports	9	Reserve alarm port
4	Reserve alarm port	10	Port LEDs
5	Console port	11	Grounding connector
6	Fan module	12	Power modules


1	System LEDs	5	10 G SFP+ port
2	Console port	6	Auxiliary port
3	PON ports	7	Port LEDs
4	1 G combo ports	-	-

Rear Panel

This section describes the rear-panel components of CGP-OLT-16T:


1	AC or DC power connector	2	Grounding connector

Ports

PON Ports

The PON ports use multi-source agreement (MSA) type UPC or SC-PC fiber connector. The PON ports support a bandwidth of 2.466 Gbps downstream and 1.244 Gbps upstream.

Console Port

The console port connects the Cisco Catalyst PON Series OLT to a PC running Microsoft Windows or to a terminal server and uses the RJ-45 crossover cable. The RJ-45 console port connection uses the supplied RJ-45-to-DB-9 female cable.

Auxiliary Port

The auxiliary port connects the Cisco Catalyst PON Series OLT to a host such as a Windows workstation or a terminal server through the auxiliary port. The auxiliary out-of-band management port is a virtual routing and forwarding (VRF) interface and uses an RJ-45 crossover cable.

1 G Combo Ports

A combo port is a combination of an SFP interface and an RJ-45 port. When the SFP interface is active, the adjacent RJ-45 port is disabled. The 1 G ports use LC connectors for fiber-optic connections and RJ-45 connectors for copper connections.

10 G SFP+ Ports

The 10 G ports use LC connector cables for fiber-optic connections and RJ-45 connector cables for copper connections. The SFP slots support only SFP+ modules. These SFP+ modules are field replaceable, and provide uplink interfaces when installed in an SFP+ module slot.

For more information on compatible Cisco SFP+ modules, see the Cisco Catalyst PON Series Switches Release Notes.

Reserve Alarm Port

The reserve alarm port connects to external monitoring systems such as the Environment Monitor System.

Note

This functionality is currently disabled.

Power Supply

The Cisco Catalyst PON Series OLT chassis has redundant power supply slots that operate with one or two power supply modules. The chassis supports field-replaceable AC-input and DC-input power supply modules.

Note

Hybrid power supply plugs are not supported.

AC Power Supply

The following table lists the power supply ratings.


Input Voltage (VAC)	Output Power (Watts)
220	100
110	100

DC Power Supply

The following table lists the power supply ratings.


Input Voltage (VAC)	Output Power (Watts)
-36 to -72VDC (with extended range upto -75VDC) Voltage differential between inputs is unlimited.	100

LEDs

You can use LEDs to monitor the activity and performance of Cisco Catalyst PON Series OLT.

Table 2. System LEDs
LED	Color	Indication
PWR1 and PWR2	Green (solid)	Normal power from power supply
PWR1 and PWR2	OFF	No power from power supply
RUN	Green (blinking)	OLT is running normally
RUN	OFF or Green (solid)	OLT is not running or OLT is running abnormally
AUX	OFF	Auxiliary port is not connected
	Green (solid)	Auxiliary port is connected, but not transmitting data
	Green (blinking)	Auxiliary port is connected and is transmitting data
OUT	Green (solid)	Power supply is normal
OUT	OFF	No power supply
FAULT	Red (Solid)	Power supply is abnormal
FAULT	OFF	Power supply is normal

Table 3. Port LEDs
LED	Color	Indication
PON port
REG	Green (solid)	ONT is registered on the OLT.
REG	OFF	No ONT is registered on the OLT.
ACT	Green (blinking)	OLT is receiving and transmitting data
ACT	OFF	OLT is not receiving and transmitting data
1 G port and 10 G port
LINK	Green (solid)	Connection is established
LINK	OFF	No connection
ACT	Green (blinking)	OLT is receiving and transmitting data
ACT	OFF	OLT is not receiving and transmitting data

Cisco Catalyst PON Series ONT Overview

The Cisco Catalyst PON Series ONT is an optical modem device that is integrated with powerful interoperability and high performance. (An ONT is also referred to as Optical Network Unit [ONU]. ONT is an ITU-T term, while ONU is an IEEE term.) The Cisco Catalyst PON ONT is located at an end user’s premises. The Cisco Catalyst PON Series ONT connects to the PON network on one side and accesses the end user's devices in FTTH, or FTTO, or FTTC service delivery architecture on the other side. The Cisco Catalyst PON Series ONT communicates between the Cisco Catalyst PON Series OLT and the end-user devices.

In the upstream direction, a Cisco Catalyst PON Series ONT is connected to the optical splitter through the PON port. The data, voice, and video signals from end user's devices are sent to the Cisco Catalyst PON Series ONT. Using the uplink ports on the Cisco Catalyst PON Series ONT, these signals are converted into electrical signals and transmitted over optical fibers to the Cisco Catalyst PON Series OLT. In the downstream direction, the Cisco Catalyst PON Series ONT is connected to various end user devices using the 1 G ports and provides triple-play services such as high-speed internet (HSI), voice (VoIP), and video (IPTV and RF overlay).

Cisco Catalyst PON Series ONT provides 1xPON port, 4x1 G 10/100/1000 PoE port, and 1xUSB Type A port with 2xForeign Exchange Station (FXS) port, and 1xcoaxial cable television (CATV) port, which is optional.