US 8,014,675 B2Granted

Passive optical network communication method and system

AssigneeOki Electric Industry Co., Ltd.

InventorsMasahiro Sarashina, Masayuki Kashima

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Abstract

A passive optical network communication system transmits an optical time-division multiplexed signal from a central office through a passive optical coupler to a number of subscribers, and transmits optical encoded signals from the subscribers through the passive optical coupler to the central office. Optical encoded signals from different subscribers are separated by a decoding process performed at the central office. All operations can be synchronized with a clock signal which is generated at the central office and recovered from the optical time-division multiplexed signal by the subscribers' equipment. The communication range can be extended inexpensively by using a single high-power light source at the central office while using relatively low-power light sources at the subscribers' equipment.

Claims14

Dependent claims

A method of communicating in a passive optical network communication system in which a central office termination unit and n subscriber termination units are linked by respective optical communication channels to a passive optical coupler, n being an integer greater than one, the method comprising:

generating an optical time-division multiplexed signal at the central office termination unit;
transmitting the optical time-division multiplexed signal through the passive optical coupler to all of the n subscriber termination units;
generating respective optical encoded signals at each of the n subscriber termination units;
transmitting the optical encoded signals through the passive optical coupler to the central office termination unit;
combining the optical encoded signals from the n subscriber termination units at the passive optical coupler into an optical code-division multiplexed signal;
transmitting the optical code-division multiplexed signal to the central office termination unit;
generating, at the central office termination unit, a time-division multiplexed signal in which data addressed to different ones of the n subscriber termination units are placed in different time slots;
converting the time-division multiplexed signal to the optical time-division multiplexed signal;
converting the optical code-division multiplexed signal to an encoded received signal at the central office termination unit;
decoding the encoded received signal by using different decoding rules to obtain data sent from different ones of the n subscriber termination units;
converting the optical time-division multiplexed signal to a received time-division multiplexed signal at each one of the n subscriber termination units;
recovering a first clock signal from the received time-division multiplexed signal at said each one of the n subscriber termination units;
extracting the data addressed to said each one of the n subscriber termination units from the received time-division multiplexed signal in synchronization with the first clock signal;
generating encoded data in synchronization with the first clock signal at said each one of the n subscriber termination units;
and
converting the encoded data, at said each one of the n subscriber termination units, to one of the optical encoded signals.

13 more elements

A passive optical network communication system in which a central office termination unit and n subscriber termination units are linked by respective optical communication channels to a passive optical coupler that transmits a first optical signal from the central office termination unit to the n subscriber termination units and transmits second optical signals from the n subscriber termination units to the central office termination unit, n being an integer greater than one, wherein:

the first optical signal is an optical time-division multiplexed signal;
the second optical signals are optical encoded signals;
the passive optical coupler combines the second optical signals from the n subscriber termination units into an optical code-division multiplexed signal which is sent to the central office termination unit, the central office termination unit including
a time-division multiplexed signal generator that generates a time-division multiplexed signal in which data addressed to different ones of the n subscriber termination units are placed in different time slots,
a first photonic element for converting the time-division multiplexed signal to the first optical signal,
a second photonic element for converting the optical code-division multiplexed signal to an encoded received signal, and
a decoding unit for decoding the encoded received signal by using different decoding rules to obtain data sent from different ones of the n subscriber termination units;
and
each one of the n subscriber termination units includes
a third photonic element for converting the first optical signal to a received time-division multiplexed signal,
a recovery unit for recovering a first clock signal from the received time-division multiplexed signal,
a demultiplexer operating in synchronization with the first clock signal to extract the data addressed to said one of the n subscriber termination units from the received time-division multiplexed signal,
an encoder operating in synchronization with the first clock signal to generate an encoded signal, and
a fourth photonic element for converting the encoded signal to one of the second optical signals.

11 more elements

Dependencies are inferred from the claim text.

Facts

Application: 12/081,631Filed 18 Apr 2008
Priority: JP 2007-14442131 May 2007
Published: US 2009/0232499 A117 Sep 2009
Granted: 6 Sep 2011
Term ends: Not estimatedThe source records don’t support an estimate.

Classification8 codes

H04J 3/1694
In which the time allocation to individual channels within a transmission cycle is variable, e.g. to accommodate varying complexity of signals,…
H04J 14/005
Optical multiplex systems: optical Code Multiplex
H04J 3/0638
Clock or time synchronisation in a network: clock or time synchronisation among nodes; Internode synchronisation
H04J 3/0685
Clock or time synchronisation in a network: clock or time synchronisation in a node; Intranode synchronisation