An Overview of ITU -T G.709

Monowar Hossain

York University

An Overview of ITU -T G.709

Introduction ITU-T G.709 Frame Structure

– Optical channel Transport Unit– Optical channel Data Unit– Optical channel Payload unit– Forward Error correction

Conclusion

Agenda

An Overview of ITU -T G.709

Interface for the Optical transport network (OTN)

Concepts borrowed from SONET/SDH– Layered structure– In-service performance monitoring– Protection– Other management function

Introduction

An Overview of ITU -T G.709

Added functionality– Management of optical channels in the optical

domain– Forward error correction (FEC) to improve error

performance and enable longer optical spans

Provides standardize method for managing optical wavelengths(channels) end to end

Introduction -continued

An Overview of ITU -T G.709

Three line Rates is defined– 2,666,057.143 kbs (optical transport unit 1)– 10,709,225.316 kbs (optical transport unit 2)– 43,018,413.559 kbs (optical transport unit 3)

Constant frame rates– 20.420 kHz (48.971 ms) for OTU1– 82.027 kHz (12.191 ms) for OTU3– 329.489 kHz(3.035 ms) for OTU3

Introduction -continued

An Overview of ITU -T G.709

Three distinct parts– Overhead area for operation, administration and

maintenance function– Pay load area for customer data– Forward error control(FEC) block

Frame Structure

An Overview of ITU -T G.709

Size – 4080 * (4 rows) bytes Data is transmitted serially beginning at the top

left first row followed by the second row and so on.

Frame Structure -continued

An Overview of ITU -T G.709

Size – 4080 * 4 rows Data is transmitted serially beginning at the top

left first row followed by the second row and so on.

Frame Structure -continued

An Overview of ITU -T G.709

Optical Transport Unit (OTU)

Frame Structure -continued

An Overview of ITU -T G.709

OTU overhead– Section Monitoring(SM) – 3 bytes– General communication channel (GCCO) – 2 bytes– Reserved (RS) – 2 bytes

Frame Structure -continued

An Overview of ITU -T G.709

Optical channel Data Unit (ODU) overhead– Reside 1-14 columns of rows 2,3 and 4– Provide tandem connection monitoring(TCM), end

to end path supervision– Client signal adaptation via the optical channel

payload unit(OPU)

Frame Structure -continued

An Overview of ITU -T G.709

Optical channel Payload Unit (OTU)– Contains information to support the adaptation of

client signal. – Located in rows 1-4 of columns 15 and 16.– Definitions very depending on the client signal being

mapped into the OPU payload.

Frame Structure -continued

An Overview of ITU -T G.709

Forward error control(FEC)– 16 FEC blocks of 16 bytes for the row. 64 bytes/frame– Reed-Solomon RS(255,239) code– Uses 16 byte interleaved codecs.– Can correct up to eight symbol errors(correction mood) and

detect up to 16 symbol errors in the code (detection mood).– Enables communications to maintain acceptable performance

quality in noisy environment.– Provide additional coded data for error checking and error

correction

Frame Structure -continued

An Overview of ITU -T G.709

Meets two requirements – To cater for the transmission needs of today’s wide

range of digital services– To assist network evolution to higher bandwidths

and improved network performance

A step further toward optical networks Question?

Conclusion