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Applications:

Passive Optical Network (PON) Test Solution

This example from the optical communication domain is about passive

optical networks (PON) based on time division multiple access (TDMA) as

used by GPON and BPON.

What is PON?

A passive optical network (PON) – specified by the full service

access network (FSAN) vendor consortium – is an access technology

for FTTx networks using small inexpensive, passive splitters, instead

of optical repeaters. In downstream direction, the signal from an

optical line terminal (OLT) is split and sent to optical network units

(ONUs). The upstream direction is more challenging for the receiver

performance testing, with signals sent from the ONUs to the OLT

using TDMA and different power levels due to different distances.

The most critical sub-module in this system is the receiver RX of the

optical line terminal (OLT) in the central office which has to deal with the

upstream signal bursts arriving from the optical network units (ONU) as

depicted in figure 1.

The SW controlling ParBERT and the other instruments can be written in

a language of your choice. It can run on the same PC that the ParBERT

SW resides on. Using e.g. visual Basic or C allows utilization of the Plug &

Play libraries provided with ParBERT (and many other instruments), which

simplifies programming.

Figure 3. ParBERT based test set-up for characterization of OLTv.

Benefits of Agilent’s ParBERT

Test accurately using:

• Exactly timed signals for data bursts and control signals

• Adjustable signal delays

• Controllable preamble states

• Superior signal quality

Test flexibly using:

• A modular multi-lane generator and analyzer platform

• Several generator/analyzer with speed classes up to 13.5 Gb/s

Subscriber ONU Central ofﬁce LT

Downstream

broadcast

Long

Guard time

Short

Upstream

TDMA

Passive

coupler

E/O

O/E

Figure 1. TDMA bursts travelling upstream on a passive optical network.

The spacing between them is very short and the amplitude may be very

different, such that the RX in the OLT must settle to the appropriate thresh-

old and synchronize its internal PLL in a very short time.

A test set-up consisting of ParBERT 81250, Agilent’s Lightwave Measure-

ment System (LMS) 8163B/8164B and a Digital Communication Analyzer

(DCA) 81600D emulating the important portions of a PON is depicted in

figure 3. ParBERT’s exact timing capability for the two data burst and the

related laser control signals is essential for standard compliant testing and

characterization of the OLT’s RX. The pattern sequencer allows the set-up

and generation of the burst-packages with desired content.

Figure 2. PON requires exact timed data bursts in an upstream test.

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