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Huawei OptiX BWS 1600G. Technical Description - part 9

4 Networking and System Applications

Table 4-2 Networking capability of type II system (C+L 80-channel, NRZ)

Classification

Specification

Typical distance

With FEC

1 × 32 dB

1 × 116 km (116 km)

Without Raman

4 × 25 dB

4 × 90 km (360 km)

amplification

7 × 22 dB

7 × 80 km (560 km)

C 800G

The C 800G system, adopting NRZ encoding and CRZ encoding (SuperWDM

technology), supports G.652 and G.655 fibers. Table 4-3 shows its networking

capability.

Table 4-3 Networking capability of type II system (C, 80-channel)

Classification

Specification

Typical distance

G.652 (with FEC)

1 × 32 dB

1 × 116 km (116 km)

5 × 25 dB

5 × 90 km (450 km)

8 × 22 dB

8 × 80 km (640 km)

G.652 (with FEC and Super

1 × 36 dB

1 × 130 km (130 km)

CRZ)

10 × 25 dB

10 × 90 km (900 km)

20 × 22 dB

20 × 80 km (1600 km)

G.655 (with FEC)

1 × 30 dB

1 × 109 km (109 km)

3 × 25 dB

3 × 90 km (270 km)

6 × 22 dB

6 × 80 km (480 km)

G.655 (with FEC and Super

1 × 32 dB

1 × 116 km (116 km)

CRZ)

6 × 25 dB

6 × 90 km (540 km)

14 × 22 dB

14 × 80 km (1120 km)

4.1.3 Type III system

The type III system, adopting NRZ encoding, is applied in G.652 or G.655 optical

fibers. Table 4-4 shows its networking capability.

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4 Networking and System Applications

Table 4-4 Networking capability of type III system (40-channel, NRZ)

Classification

Specification

Typical distance

With FEC

1 × 34 dB

127 km (127 km)

Without Raman

5 × 27 dB

5 × 98 km (490 km)

amplification

10 × 22 dB

10 × 80 km (800 km)

Table 4-5 shows the networking capability of the system when it adopts

SuperWDM technology (CRZ encoding) and is applied in G.652 optical fibers.

Table 4-5 Networking capability of type III system (40-channel, SuperWDM)

Classification

Specification

Typical distance

With FEC

10 × 27 dB

10 × 98 km (980 km)

Without Raman

25 × 22 dB

25 × 80 km (2000 km)

In ultra-long distance transmission, non-flatness of optical power and dispersion

will occur to each channel. If there are more than 12 optical amplification spans, the

system should be equipped with the OEQ. If the distance of the fiber in multiplex

section exceeds 1000 km, the system should be equipped with dispersion

equalization equipment.

If the system adopts Raman amplification or AFEC, the system performance will be

improved, thus enhancing the transmission capability over single hop.

The specifications listed in Table 4-4 and Table 4-5 show the application of type III

in G.652 and G.655 optical fibers. For G.653, the proper wavelengths and input

optical power should be selected in C-band to avoid the mixing of four wavelengths.

Table 4-6 shows the application of type III system in G.653 optical fibers.

Table 4-6 Networking capability of type III system (G.653 optical fiber)

Classification

Specification

Typical distance

With FEC

1 × 32 dB

1 × 116 km (116 km)

12-wavelength system

3 × 27 dB

3 × 98 km (294 km)

6 × 23 dB

6 × 83 km (498 km)

With FEC

1 × 33 dB

1 × 120 km (120 km)

8-wavelength system

3 × 28 dB

3 × 100 km (300 km)

8 × 20 dB

8 × 70 km (560 km)

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4 Networking and System Applications

4.1.4 Type IV system

The type IV system, adopting L-band signal, is specially used in G.653 optical

fibers.

This system adopts NRZ encoding. Its networking capability is shown in Table 4-7.

Table 4-7 Networking capability of type IV system (40-channel, L band)

Classification

Specification

Typical distance

With FEC

1 × 30 dB

1 × 109 km (109 km)

3 × 25 dB

3 × 90 km (270 km)

5 × 22 dB

5 × 80 km (400 km)

If the system adopts the Raman amplifier, the noise will be greatly reduced, thus

realizing longer transmission without a regenerator.

4.1.5 Type V system

The type V system, adopting NRZ encoding, is applied in G.652 or G.655 optical

fibers. Table 4-8 shows its networking capability.

Table 4-8 Networking capability of type V system (40-channel, NRZ)

Classification

Specification

Typical distance

With FEC

1 × 39 dB

1 × 140 km (140 km)

6 × 27 dB

6 × 98 km (588 km)

8 × 22 dB

8 × 80 km (640 km)

The type V system can realize transmission of 640 km without using the REG and

any dispersion compensation component. Generally, the type V system does not

need Raman amplification.

4.1.6 Type VI system

The type VI system is an LHP (Long Hop) system, applied in G.652 or G.655

optical fibers. Its networking capability is shown in Table 4-9.

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4 Networking and System Applications

Table 4-9 Networking capability of type VI system (NRZ)

Application

Single wavelength rate: 10 Gbit/s

Single wavelength rate: 2.5

Gbit/s

Classification

10-wavelength

40-wavelength

10-wavelength

40-wavelength

OSNR requirement

20 dB

18 dB

20 dB

18 dB

15 dB

HBA + FEC + Raman

50 dB

53 dB

43 dB

46 dB

56 dB

49 dB

Note: The OSNR in the table is the requirement at the point MPI-R. The OSNR requirements are typical values.

Table 4-10 System transmission specifications of type VI system with ROPA

Equipment

Single wavelength: 10 Gbit/s

Single wavelength: 2.5 Gbit/s

10-wavelength

40-wavelength

10-wavelength

40-wavelength

Sub-System

NRZ

CRZ

NRZ

CRZ

ROPA+LHP. R001

60 dB

51 dB

64 dB

55 dB

ROPA+LHP, G.652 fibre

61 dB

65 dB

51 dB

54 dB

65 dB

57 dB

in the line

ROPA+LHP, R002 with

61 dB

64 dB

51 dB

54 dB

65 dB

57 dB

G.655(LEAF) fibre in the

line

Notes: Table 4-10 lists the basic specifications. If other specifications are required, contact Huawei Technologies Co. Ltd.

(hereinafter referred to as Huawei).

The LHP system is point-to-point OTM configuration without any optical or

electrical regeneration.

If the SuperWDM technology is used, the transmission distance can be extended.

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4 Networking and System Applications

4.2 System Functions

4.2.1 Automatic Level Control

Function Description

In a DWDM system, optical fiber aging, optical connector aging or human factors

might lead to the abnormal attenuation of transmission lines.

In case the attenuation on a line segment increases, all input and output power will

be reduced on all downstream amplifiers. The system OSNR will get worse. At the

same time, the received optical power will also be reduced. Receiving performance

will be greatly affected. The closer the attenuated segment is to the transmit end, the

more influence on OSNR there will be, as shown in Figure 4-2.

If the automatic level control (ALC) function is activated, this effect can be

minimized. As the attenuation on a line segment is increased, the input power on the

amplifier will be reduced. But due to ALC, the output power as well as the input

and output powers of other downstream amplifiers will not be changed. Hence there

will be much less influence on OSNR. The optical power received by the receiver

will not be changed.

Figure 4-3 shows the power changes on optical line amplification regenerators in

the gain control and the power control modes in case of abnormal attenuation on

optical fiber lines.

High line losses

OAU

Normal output

Attenuated output

Attenuated input

Figure 4-2 System power when ALC is not activated

High line losses

OAU

Normal output

Normal input

Attenuated input

Figure 4-3 System power when ALC is activated

In normal working, two elements might cause the input power change in the optical

amplifier:

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4 Networking and System Applications

The addition/reduction of access channels (multiple channels might be added

or dropped at the same time)

In order not to affect the normal working of other channels, the system should

quickly respond to the change. The system works in the gain control mode.

The abnormal attenuation in the physical media

ALC determine the adjustment of the variable optical attenuator according to the

channel amount and output power.

The redundancy design of the system permits the abnormal line attenuation

adjustment. If the attenuation is within the limit, the adjustment process will take

several minutes.

It ensures the normal working of the system.

ALC is realized through channel amount detection and reference power.

Channel Amount Detection

Prerequisite: One MCA needs to be configured on the ALC link.

Realization:

The optical amplifier works in automatic gain control (AGC) mode and realizes

ALC function with MCA. The MCA analyzes the amount of working channels.

Based on the amount of channels and the output power, the optical amplifier

determines the working status and adjusts attenuation to keep the output power

stable (the power of a single channel remains unchanged).

Reference Power Detection

Prerequisite: The output optical power of the first node on the ALC link is taken as

a reference value.

Realization: The optical amplifier works in AGC mode, by activating the detection

of the output optical power of the optical amplifier at the first node to determine

further actions. Compare the detecting result with the information reported before

the ALC command is trigged. If they are consistent, deliver the ALC adjustment

command formally to adjust attenuation and to keep the output optical power stable.

(The power of a single channel remains unchanged.)

Involved Boards

Boards of the following types are involved in the ALC.

Detection board

The MCA is included.

The detection board detects signals of all channels at the receive end.

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4 Networking and System Applications

In channel amount mode, the board provides the system with the wavelength

amount of the network.

Optical amplifier board

The OAU and the OBU are included.

When the ALC is enabled, the output power of optical amplifier boards is detected

to check if the link is abnormal.

Attenuation adjusting board

The OAU, VOA, and the VA4 are included. They adjust the line attenuation.

The OAU is an optical amplifier board but can function as an adjusting board

because of its VOA.

Supervisory channel board

The SC1/TC1 and the SC2/TC2 are included.

The supervisory channel board provides supervisory channel connection and the

physical channel to transmit protocol frames.

SCC board

The SCC functions as the executive board for the ALC function.

Ethernet port

The Ethernet port provides inter-subrack communication. When the link in L-band

is configured, the ALC protocol frames are transmitted in the protocol transmission

channel of C-band. This is because the L-band has no protocol transmission

channel. The protocols need to be transmitted between subracks of the C-band and

of the L-band.

The Ethernet interface is used for inter-subrack connection. In subracks, only the

"Ethernet 2" interface is available for protocol transmission.

4.2.2 Intelligent Power Adjustment

Function Description

The OptiX BWS 1600G system provides the intelligent power adjustment (IPA)

function.

In case the optical power signals on one or more segments of the active optical path

are lost, the system can detect the loss of optical signals on the link and instantly

reduce the optical power of the amplifier before the loss to a safety level.

If there are raman amplifiers in the link, it will be shut down also.

When the optical signals are restored to normal, the optical amplifier will work

again. The loss of optical signals might be caused by fiber cut, equipment

deterioration, or connector disconnections.

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4 Networking and System Applications

Note

In the DWDM system, the IPA function is started only when optical signals of the

active optical path are lost.

When this function is executed, only the lasers on the main path are shut down. No

operation will be implemented on the optical supervisory channel. Hence the

functions of all optical supervisory channels are not affected.

Fiber Break Detection

There are three methods used to detect the fiber break to achieve the IPA function.

Detect the LOS of the optical amplifier unit

Detect the signals of the Auxiliary detection unit (OSC/OTU)

Detect the LOS of the raman amplifier unit (RPC)

Through a combination of the three methods, the fiber break can be judged more

correctly.

Following is the logic of problem handling.

If all the configured detection items meet the fiber break condition at the

same time, initiate the shut down process of the IPA.

If one of the detection conditions recovers to normality, initiate the recovery

process of the IPA.

Configuration Precaution

When the amplifiers are configured as detection unit independently, IPA must

only be configured at the first site and the last site of the link. When there is a

fiber break, the amplifier at the first site and the last site of the link will be

shut down.

To fulfill the IPA function and judge the fiber break more correctly, detection

unit and auxiliary detection unit must be configured at the same time. IPA

must be configured at every site. When there is a fiber break, the amplifier

before and after the fiber break will be shut down.

4.2.3 Automatic Power Equilibrium

Function Description

The automatic power equilibrium (APE) function can automatically adjust optical

power of each channel at the transmit end. This is to optimize the OSNR at the

receive end.

In a DWDM system, the variety of the optical fiber condition in the running of the

system may change the flatness of a channel’s power from that in the

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4 Networking and System Applications

commissioning, and degrade the Optical Signal Noise Ratio (OSNR) of signals at

the receive end, as shown in Figure 4-4.

With the Automatic Power pre-Equilibrium (APE) function provided by the system,

you can enable the system to automatically adjust the optical power of the transmit

end of each channel to keep the flatness of the optical power of the receive end

close to that in the commissioning and to maintain the OSNR, as shown in Figure

4-5.

flatness of the optical power

at the recieve site

OTM

OLA

OADM

OEQ

OTM

Figure 4-4 Flatness of the optical power at the receive end when APE is not activate

flatness of the optical power

at the recieve site

OTM

OLA

OADM

OEQ

OTM

Figure 4-5 Flatness of the optical power at the receive end when APE is activate

The application of the APE streamlines the operation of the DWDM system

commissioning and subsequent network maintenance for the operator.

The design of starting regulation manually facilitates the operator to determine

whether to adjust the optical power according to the network actual status.

In following example, the APE function is realized by the MCA, V40, SC1 and

SCC.

The networking is shown in Figure 4-6.

OTU

V40

D40

OTU

SC1

MCA

OTU

D40

M40

OTU

adjustment station

monitoring station

Figure 4-6 Networking for APE function

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4 Networking and System Applications

The normal function of APE requires the coordination between the service boards

and the SCC board, and the participation of the user.

As shown in Figure 4-6, for power equilibrium, each channel power at the transmit

end can be adjusted according to the per channel power measured by the MCA at

the receive end. The APE brings convenience to DWDM system tests in

deployment and subsequent network maintenance. The APE function mode can

also be set to allow users to decide whether to adjust the optical power.

Implementation Principles

To implement the APE, follow the steps below:

During the commissioning, apply manual adjustment on the adjustment unit

to restore each channel.

After the commissioning, save the power curve of the receive end as the

standard power curve.

Detect optical power of every channel received by the detection unit (such as

MCA) through the optical port at the receive end.

According to the detected optical power of every channel, adjusts the

attenuation rate of the according channel of the adjust unit (such as V40) at

the transmit end, so as to maintain the optical signal-to-noise ratio (OSNR) of

every channel at the receive end by keeping the flatness of the optical power

of every channel.

Note

During the running of the equipment, the MCA analyzes the data scanned in a

spectral scanning period, which is set in the MCA configuration and is not provided

in the APE.

If the power offset exceeds the threshold configured, the system will report the

event of optical power unbalance and the user determine whether to adjust it

according to the network condition.

Involved Boards

The APE functions through service board and the SCC board. The APE involves

board s of the following types:

Detection board

It detects the signal power of the channels at the receive end and reports APE

uneven event.

The MCA functions as the detection board in the system.

Adjustment board

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It is the adjusting entity of the APE and adjusts the attenuation of channels.

The V40 or the DGE functions as the adjustment board in the system.

Supervisory channel board

It provides the supervisory channel and the physical channel for protocol frame

transmission.

The SC1/TC1 or the SC2/TC2 functions as the supervisory channel board.

System control and communication board

It is the executive entity of the APE.

The SCC functions as the system control and communication board.

Configuration principle

APE is optional and configured on the users’ requirement.

For the APE function, it is required that the OTM station at the transmit end

should be configured with the V40 or the OEQ station should be configured

with DGE and MCA, and the OTM station at the receive end should be

configured with the MCA. Moreover, since DWDM is a dual-fiber

bidirectional system, an MCA should be configured at the both ends of a

multiplex section.

The optical power adjustment is realized in two ways. The V40 adjusts the

optical power of the corresponding channel at the transmit end. The DGE of

optical equilibrium (OEQ) station adjusts the optical power of the

corresponding channels. The optical measurement is realized by using the

MCA in OEQ or OTM station.

To implement the APE function by the DGE board on the OEQ station, when

configure the DGE board in T2000. It is required to select the DGE board in

the "Power Regulating Subrack of EVEN wavelength" and "Power Regulating

Unit of EVEN wavelength" drop-down lists of the "Create APE Pair"tab.

To realize the APE function, it is required to install the MCA and OSC unit

(SC1/SC2/TC1/TC2) in one subrack. If not, the network port ETHERNET 2

of two subracks should be interconnected.

To realize the APE function, it is required to install the V40 and OSC unit

(SC1/SC2/TC1/TC2) in one subrack. If not, the network port ETHERNET 2

of two subracks should be interconnected.

Precautions of the configuration

Here we define a station as an adjustment station where optical power is

adjusted and define a station as a monitoring station where optical power is

measured by the MCA.

To start the APE function, the V40 or DGE of the adjustment station and one

of optical interfaces of the MCA of the monitoring station should be first

configured as an APE function pair, and enable APE function.

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