The same clocking reference at both ends of the DS1 or E1 link is required to meet the wander requirements of TDM traffic.
The business ONU can use one of two clocking sources for CES:
•
a derived GPON clock at 16.384 MHz9 — ISAM Support for the GPON ONU
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The downstream TDM streams may be timed from one of two clocking sources:
•
a 16.384 MHz adaptive clock received from the CES packet stream.•
a differential clock recovered from the CES packet stream via the GPON. When the clock is received from the GPON, the GPON must be configured to send RTP packets.In adaptive timing, a local, free-running 25 MHz clock is used. The generated bit rate is determined by the long-term average data rate. The attached DS1/E1 equipment must be loop-timed. In differential timing, a 16.384 MHz reference clock is synchronized to the PON. Both ends of the DS1/E1 CES PW must use the same reference clock frequency and be synchronized to a common source. RTP is used to transport the transmitted bit rate information. The DS1 or E1 equipment that is attached to the terminating CES PW devices must be loop-timed. In loop timing, the received clock rate is used for the transmitted clock rate. The DS1/E1 equipment that is attached must be source-timed, not loop-timed.
Timestamps within the CES packets are used for carrying timing information across the network. Timestamp values are generated in differential format when the interface is operating in differential timing reference mode. Otherwise, the timestamp values represent absolute time.
An RTP header can be added to each CES packet for timing purposes and determine whether or not to include the 4 byte control word immediately preceding the RTP header.
Configure RTP header parameters using a CLI, a TL1 or an AMS management session with the P-OLT
9.7
Video Overlay
The ISAM can provide RF video service through the video overlay function. The function operates downstream in the 1550 nm optical band. Signals sent over the overlay network are presented to the subscriber as RF signals from a video F-type connector in the ONU.
The RF video service in the downstream 1550 nm optical band supports most available cable television (CATV) services, including standard analog broadcast channels, as well as standard and high definition digital broadcast channels. In the upstream direction, the 1310 nm return channel is carried over an HSI service. For access to these services, a set-top box may be required between the video output of the ONU equipment and the customer's television set.
Within the ONU functional blocks, the RF subsystem is an RF amplifier that produces the required RF output for the subscriber video equipment. The RF subsystem monitors the levels of optical and RF signals in support of the performance management functions. The RF video service is optional and independent of the SoC functions.
9 — ISAM Support for the GPON ONU
Figure 9-3 Video overlay service in ISAM
9.8
Home Phoneline Network (HPNA)
HPNA is a subscriber interface that is preferred by some service providers. The technology allows the service provider to deploy high bandwidth services (> 10 Mb/s) without the need to install CAT5 wiring in older homes that were not wired for broadband services. Two options exist to match the possible subscriber's wiring:
•
HPNA over twisted pair•
HPNA over COAX.HPNA is an integrated protocol stack handling PHY, Data Link, Convergence and Management Layers. The HPNA protocol provides a synchronous, collision-free media access method. A master device on the network control access to the network and periodically registers devices on the network. Devices compatible with version 3.1 of the HPNA standards are backwards compatible with previous versions of HPNA.
HPNA over Twisted Pair provides relatively broadband services over CAT3 or better wiring. This HPNA physical layer is compatible with POTS, V.90 and various other protocols. Coax Ethernet Coax Coax ISAM VoD server WDM Router IP Network Broadcast video Analog channels Digital channels VoD Ethernet Private network Video optical transmitter EDFA
PowerProcessorMajor Alarm Minor Alarm
Video head end Core transport Central office Fiber (PON) Distribution
ONT Home network
1550 nm (downstream RF video) 1310 nm (upstream) 1490 nm (downstream data) Video RF mux
Analog broadcast No STB needed
A
A
Digital broadcast STB needed B
Broadcast and VoD STB needed C
B
9 — ISAM Support for the GPON ONU
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•
G.9954 “Home networking transceivers - Enhanced physical, media access, and link layer specifications”•
The throughput:•
Bi-directional throughput over the HPNA port shall be at least 38 Mbps in each direction for 1514 byte packets.•
Unidirectional throughput over the HPNA port shall be at least 96Mbps.9.9
Power over Ethernet
Power over Ethernet (PoE) technology describes a system to pass electrical power safely, along with data, on Ethernet cabling. Power is supplied in common mode over two or more of the differential pairs of wires found in the Ethernet cables and comes from a power supply within a PoE-enabled networking device such as an Ethernet switch or can be injected into a cable run with a midspan power supply.
The IEEE standard for PoE requires Category 5 cable or higher for high power levels, but can operate with category 3 cable for low power levels.
The IEEE 802.3af-2003 PoE standard provides up to 15.4 W of DC power (minimum 44 V DC and 350 mA) to each device. The IEEE 802.3at PoE standard also known as PoE+ or PoE plus, provides up to 25.5 W of power. PoE is presently deployed in applications where USB is unsuitable and where AC power would be inconvenient, expensive or infeasible to supply. Foe example, PoE is especially useful for powering IP telephones, wireless LAN access points, cameras with pan tilt and zoom (PTZ), remote Ethernet switches, embedded computers, thin clients and LCDs which is approximately 100 m of cable.
PoE has several advantages, including:
•
Cheaper cabling•
A true gigabit connection to every device is possible•
Global organizations can deploy PoE everywhere without concern for any local variance in AC power standards, outlets, plugs, or reliability.The PoE interface of the ISAM complies with IEEE 802.3at, and is backwards compatible with IEEE802.3 af.
•
PoE supported through FE ports9.10
Ethernet loopback detection
The GPON ONU supports the loopback detection in the same Ethernet port or different Ethernet ports.
The GPON OLT allows you to enable or disable the function per ONT.
When a loopback is detected on the ONU side, the ONU will trigger an alarm and send it to the OLT. The OLT reports the alarm messages to the AMS. The alarm will be cleared by the ONU when the loopback issue is resolved.
9 — ISAM Support for the GPON ONU
The OLT can be configured to enable or disable the action of shutting down the port where the loopback exists. Depending on the configuration, the ONU or the OLT will shutdown the port.
9 — ISAM Support for the GPON ONU