Management, monitoring and performance optimization of optical networks

• US 9,054,832 B2
• Filed: 12/06/2010
• Issued: 06/09/2015
• Est. Priority Date: 12/08/2009
• Status: Active Grant

• Current Assignee: Snell Holdings, LLC (Treq Labs, Inc.)
• Original Assignee: Treq Labs, Inc.
• Inventors: Barnard, Chris Wilhelm, Myslinski, Piotr, Wright, Colin John
• Primary Examiner(s): Li, Shi K
• Application Number:
  US12/961,439
• Publication Number:
  US 20110158642A1
• Time in Patent Office: 1,646 Days
• Field of Search: 398/16, 398 25- 29
• US Class Current: 1/1
• CPC Class Codes: H04B 10/0793 Network aspects, e.g. central monitoring of transmission parameters
• CPC Class Codes: H04B 10/572 Wavelength control
• CPC Class Codes: H04J 14/02 Wavelength-division multiplex systems
• CPC Class Codes: H04J 14/0201 Add-and-drop multiplexing
• CPC Class Codes: H04J 14/0287 Protection in WDM systems
• CPC Class Codes: H04J 14/0293 Optical channel protection
• CPC Class Codes: H04L 45/28 using route fault recovery
• CPC Class Codes: H04L 45/50 using label swapping, e.g. multi-protocol label switch [MPLS]
• CPC Class Codes: H04Q 11/0066 Provisions for optical burst or packet networks
• CPC Class Codes: H04Q 2011/0081 Fault tolerance; Redundancy; Recovery; Reconfigurability

Abstract

The present invention includes novel techniques, apparatus, and systems for optical WDM communications. Tunable lasers are employed to generate respective subcarrier frequencies which represent subchannels of an ITU channel to which client signals can be mapped. In one embodiment, subchannels are polarization interleaved to reduce crosstalk. In another embodiment, polarization multiplexing is used to increase the spectral density. Client circuits can be divided and combined with one another before being mapped, independent of one another, to individual subchannels within and across ITU channels. A crosspoint switch can be used to control the client to subchannel mapping, thereby enabling subchannel protection switching and hitless wavelength switching. Network architectures and subchannel transponders, muxponders and crossponders are disclosed, and techniques are employed (at the subchannel level/layer), to facilitate the desired optical routing, switching, concatenation and protection of the client circuits mapped to these subchannels across the nodes of a WDM network.

Claims

1. An improved method for monitoring the performance of optical networking equipment used to transmit signals among a plurality of nodes interconnected by one or more fiber optic cables to form an optical network, the method comprising:

(a) selecting one or more performance metrics to monitor with respect to signals transmitted over the network from an optical transmitter at a first node to an optical receiver at a second node;

(b) selecting an unused communications channel as a monitor channel to measure the selected performance metrics against a predefined acceptable level of tolerance;

(c) selecting an available signal channel to transmit signals from the transmitter at the first node to the receiver at the second node;

(d) tuning the transmitter initially to the selected monitor channel to measure the selected performance metrics for signals transmitted from the transmitter at the first node to the receiver at the second node; and

(e) switching the transmitter from the selected monitor channel to the selected signal channel upon determining that the measured performance metrics are within the predefined acceptable level of tolerance;

(f) further including the step of measuring the polarization mode dispersion of an optical path in the optical network via the following steps;

(g) measuring a first phase difference between a first signal and a second signal transmitted along the optical path, where the frequency spacing between the first and second signals is known, and the polarizations of the first and second signals are aligned along a first polarization axis at the transmitter end of the optical path;

(h) measuring a second phase difference between a third signal and a fourth signal transmitted along the optical path, where the frequency spacing between the third and fourth signals is known, and the polarizations of the third and fourth signals are aligned along a second polarization axis at the transmitter end of the optical path; and

(i) calculating the difference between the first and second phase differences.

2. The method of claim 1, wherein OSC management communications include the results of measuring the selected performance metrics via the monitor channel, and wherein the OSC management communications are routed among nodes of the optical network, based on current network conditions, by utilizing (i) a dedicated out-of-band channel, (ii) the overhead portion of an existing in-band communications channel, or (iii) the unused payload portion of an existing in-band communications channel.

3. The method of claim 1, further including the step of measuring the chromatic dispersion of an optical path in the optical network by measuring the received phase difference between two transmitters with a known optical frequency spacing transmitted over the optical path.

4. The method of claim 1, further including the step of measuring the optical signal to noise ratio of an optical path in a fiber network by measuring the difference in received power levels, at the output of a narrow-band receiver filter, from (a) a first laser tuned to the center of the receiver filter and (b) a second laser tuned away from the passband of the receive filter.

5. The method of claim 1, further including the following steps to add signals to the optical network without disrupting live traffic:

(a) monitoring a first set of performance metrics with respect to a first signal on the network;

(b) adding a second signal to the network, during the monitoring of the first set of performance metrics, by gradually increasing the output power of a transmitter used to transmit the second signal onto the network;

(c) terminating the increasing of the output power of the transmitter when the first set of performance metrics reaches a predefined performance target value; and

(d) generating an alarm if a predefined alarm threshold value is exceeded.

6. The method of claim 5, further including the step of equalizing the optical signal to noise ratio (OSNR) across the network by determining, as each new signal is provisioned, a current OSNR value as a function of the OSNR of existing signals, and increasing the power output of the new signal until its OSNR reaches the current OSNR value.

7. The method of claim 5 wherein the first set of performance metrics includes a bit error rate.

8. The method of claim 1, further including the step of automatically providing diagnostic data to a user of networking equipment containing a plurality of digital registers by:

(a) receiving a predefined expected value with respect to each of a first subset of the plurality of digital registers;

(b) automatically retrieving the actual value stored in each of the first subset of digital registers;

(c) comparing the retrieved actual values with their predefined expected values; and

(d) reporting the differences between the actual values and the expected values to the user.

9. The method of claim 1, further including the step of optimizing the power level of an optical receiver via a power control circuit that comprises (i) an optical doped-fiber preamplifier;

and (ii) a variable optical attenuator (VOA) having two inputs, wherein the output of the optical doped-fiber preamplifier is connected to the first input, and an attenuation signal is connected to the second input to automatically attenuate the output of the preamplifier so as to maintain the power level of the optical receiver at a predefined optimum power level.

10. The method of claim 1, further including the following steps to determine a path of a signal transmitted from the first node to the second node:

(a) connecting an output filter having a plurality of output ports to the output of an optical transmitter that transmits the signal; and

(b) tuning a transmit laser within the transmitter to a predefined frequency to select the output port of the output filter through which the signal will be transmitted onto the network;

(c) whereby the path of the signal through the network is effectively determined by the predefined frequency.

11. The method of claim 1, further including the following steps to maintain an optimum power level of the optical receiver:

(a) defining an optimum power level with respect to the optical receiver;

(b) connecting the output of an optical doped-fiber preamplifier to a first input of a variable optical attenuator (VOA); and

(c) connecting an attenuation signal to a second input of the VOA to automatically attenuate the output of the preamplifier so as to maintain the power level of the optical receiver at the optimum power level.