OTN Introduction
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P-0
Op tical t ran spo rt h ie rarch y ………………………………………………Pa ge4
OTN interface structure…………………………………………………..Page8
Multiplex ing/mapping principles an d bit rates ……………...……….Page14
Overhead description……………………………………………………Page19
Maintenance signals and function for different layers………………..Page39
A l a rm an d pe r fo rm an c e ev en ts ………… ……… ……… …… …… … . P a g e5 0
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OTN Introduction
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P-1
This Course is mainly based on：
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ITU-T G.872
Architecture of optical transport networks
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ITU-T G.709
Interfaces for the Optical Transport Network (OTN)
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ITU-T G.874
Management aspects of the optical transport network element
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ITU-T G.798
Characteristics of optical transport network hierarchy equipment
functional blocks
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OTN Introduction
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Reference:
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ITU-T G.709
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P-2
OTN Introduction
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Objectives for this chapter:
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Describe the features of OTN
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Outline the protocols which supports OTN system
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P-3
OTN Introduction
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P-4
One important feature of OTN is that the transmission setting of any digital customer
signal is independent of specific features of the customer, that is, independence of
customer.
According to the requirements given in Rec. G.872.
The optical transport network supports the operation and management aspects of optical
networks of various architectures.
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OTN Introduction
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P-5
Compared with SDH/SONET, the benefits of OTN are as follows:
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Strong scalability of the capacity: The cross-connect capacity can be expanded to
dozens of T bit/s.
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The customer signal transparency covers payload and clock information.
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The asynchronous mapping eliminates restriction on the synchronization in the
whole network, with stronger FEC. The simplified system design can decrease the
networking costs.
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Up to 6-level TCM monitoring management capability.
Compared with the traditional WDM:
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Effective monitoring capability: OAM&P and network survivability
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Flexible optical/electrical grooming capability, carrier-class, manageable, and
operable networking capability.
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OTN Introduction
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P-6
G.874, management features of optical transmission NE, describes the management
feature of the OTN NE and transmission function of one or more network layers in the
OTN. The management of the optical layer network is separated from the management of
the customer layer network. Therefore, the same management method that is
independent of the customer can be used. G.874 defines fault management, configuration
management, billing management, and performance monitoring. G.874 describes the
management network architecture model between the NE EMS and optical NE equipment
management functions.
G.798, feature of equipment function block of the optical transport network, defines the
function requirements of the optical transmission network in the NE equipment.
G.709, OTN interface, defines OTM-n signal requirements of OTN, including OTH, support
of multi wavelength optical network overhead, frame structure, bit rate, and format of
mapping customer signals.
G.872, OTN architecture, defines the relation between OTN hierarchical architecture,
feature information and customer/service layer, and the function description of the
network topology and layer network.
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OTN Introduction
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Objectives for this chapter:
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Draw the frame structure of OTN;
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Outline the function of each part in OTN frame;
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Brief introduce the difference between OTM-n.m and OTM-0.m;
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Describe how does a client signal are encapsulated to OTN frame.
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P-7
OTN Introduction
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P-8
Customer signals (for example, IP/MPLS, ATM, Ethernet, and SDH signals), served as OPU,
plus the OPU payload are mapped to the OPUk, where, k is 1, 2, 3. k=1 indicates that the
bit rate is about 2.5 Gbit/s, k=2 indicates that the bit rate is about 10 Gbit/s, and k=3
indicates that the bit rate is about 40 Gbit/s.
OPUk is added as the ODU payload. After ODUkP, ODUkT, frame alignment overhead, and
all-zero OTU overhead are added, the ODUk is formed.
ODUk is combined into the OTU overhead and FEC region, and then mapped to the
completely standardized optical channel transport unit k – OTUk, or standardized function
optical channel transport unit k – OTUkV.
The OTUk is combined into OCh, and then mapped to the OCh with complete functions
or, and simplified function optical channel OChr.
After the OCh is modulated to the optical channel carrier (OCC), n OCCs performs the
Wavelength Division Multiplexing (WDM), and then are combined into the OMS overhead
to form the OMSn interface.
After the OMSn is combined into the OTS overhead, the OTSn unit is formed.
The OChr is modulated to the OCCr. N OCCr perform the WDM to form the optical
physical section OPSn. The OPSn is combined with the OMS without the monitoring
information and the transport function of the OTS layer network.
To be continued in the next page
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OTN Introduction
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P-9
The figure on the right shows the composition of the OTM-n.m signals of the OTM
interface with complete function. The OTM-n.m is composed of up to n multiplexing
wavelengths and OTM overhead signals that support the non-associated overhead, m can
be 1, 2, 3, 12, 23, or 123.”m=1” indicates the signals are OTU1/OTU1V. m=2: indicate the
signals are OTU2/OTU2V. “m=3” indicates the signals are OTU3/OTU3V. “m=12” indicates
partial signals are OTU1/OTU1V and partial signals are OTU2/OTU2V. “m=23” indicates
partial signals are OTU 2/OTU2V and partial signals are OTU3/OTU3V. “m=123” indicates
partial signals are OTU 1/OTU1V, partial signals are OTU2/OTU2V, and partial signals are
OTU3/OTU3V. The physical optical feature specifications of OTM-n.m signals are
determined by the suppliers. The recommendations do not have specific specifications.
The optical layer signal OCh is composed of OCh payload and OCh overhead. After the
OCh is modulated to the OCC, multiple OCC time division multiplexes (TDM) constitute the
OCG-n.m unit. OMSn payload and OMSn overhead constitute the OMU-n.m. OTSn
payload and OTSn overhead constitute the OTM-n.m unit.
The overhead and generic management information of the optical layer units constitute
the OTM overhead signal (OOS), which is transmitted by 1-channel independent OSC in
the non-associated overhead.
The overhead of electrical layer units such as OPUk, ODUk, and OTUk are the associated
channel overheads, which are transmitted together with the payload.
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OTN Introduction
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P-10
The OTM-nr.m signals are composed of up to n optical channel multiplexing, and does not
support the non-associated overhead. At present, m of OTM-16r.m can be 1, 2, 3, 12, 23,
or 123, where, the physical optical feature specifications of OTM-16r.1 and OTM-16r.2 are
defined in G959.1 of ITU-T. The physical optical feature specifications of other four signals
are in need of the further study.
The electrical layer signal structures of OTM-nr.m and OTM-n.m are the same. The optical
layer signals do not support the non-associated overhead OOS, without the optical
monitor channel. Therefore, it is called the OTM interface with the reduced function.
This OTM-16r.m supports 16 optical channels on a single optical span with 3R
regeneration at each end. The OTM-16r.m signal is an OTM-nr.m signal with 16 optical
channel carriers (OCCr) numbered OCCr #0 to OCCr #15. An optical supervisory channel
(OSC) is not present and there is no OOS either.
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OTN Introduction
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Objectives for this chapter:
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Draw the mapping route of OTM;
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List the rate of all types of OTUk,ODUk and OPUk signals;
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Describe how does a lower rate ODUk multiplex to a higher rate ODUk.
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P-11
OTN Introduction
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P-12
Customer signals or ODTUGk is mapped to OPUk; OPUk is mapped to ODUk; ODUk is
mapped to OTUk or OTUkV; OTUk or OTUkV is mapped to OCh or OChr. Finally, OCh or
OChr is modulated to OCC or OCCr.
The multiplexing includes the TDM from low-level ODU to high-level ODU and the WDM
from up to n OCC or OCCr to one OCG-n.m or OCG-r.m (here, n ≥1).
The TDM is used to transmit multiple low-rate optical channel signals on one high-rate
optical channel, and to perform the end-to-end path maintenance for these low-rate
channels. Through the TDM, up to four ODU1 signals can be multiplexed to one ODTUG2.
Then, the ODTUG2 is mapped to the OPU2. Meanwhile, j ODU2 and 16-4j ODU1 signals
can be multiplexed to one ODTUG3, where j≤4. ODTUG3 is mapped to OPU3. OPU2 and
OPU3 can be multiplexed to the corresponding large granularity customer signals.
For the WDM, the OCC or OCCr unit of OCG-n.m or OCG-r.m can adopt various rates.
OTM-n.m or OTM-r.m transmits OCG-n.m or OCG-r.m. In addition, OTM-n.m interface can
multiplex the OSC to the OTM-n.m through the WDM.
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OTN Introduction
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P-13
As we know,the size of OTUk is fixed, that is, OTU1, OTU2, and OTU3 are 4-line and
4080-column. For OTU1 frames, from Column 1 to Column 16, there are OTU1, ODU1,
and OPU1 overhead. From Column 17 to Column 3824 (with 3808 columns in total), there
are customer signals. From column 3825 to column 4080 (with 256 columns in total),
there are FEC areas. Assume the customer signals are STM-16 SDH signals, the rate is 2
488 320kbit/s, the calculations are as follows:
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Customer signal /OTU frame = Customer signals rate / nominal OTU frame rate
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3808/4080 = 2 488 320 / nominal OTU1 frame rate
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That is, nominal OTU1 frame rate = 255/238 x 2 488 320 kbit/s
For OTU2 frames, four ODU1s are combined to ODTUG2 through the TDM. Four ODU1s
operate as the OPU2 payload, occupying 3808 columns. In OPU2 payload, there are 16
columns of OTU1, ODU1, and OPU1 overhead. Therefore, the customer signals are 3792
columns. The calculation is as follows:
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3792/4080 = 2 488 320 x 4 / nominal OTU2 frame rate
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That is, nominal OTU2 frame rate = 255/237 x 9 953 280 kbit/s
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The nominal OTU3 frame rate = 255/236 x 39 813 120 kbit/s
For OTU1/2/3 frame rate, the conclusion is as follows:
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OTUk rate = 255/(239-k) x STM-N frame rate , k=1, 2, 3 correspond to the frame
rate of STM-16, STM-64, and STM-256 respectively.
The OTU bit rate tolerance is ± 20 ppm.
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OTN Introduction
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P-14
Two customer/service relationships are defined:
One ODU2 transmits four ODU1.
One ODU3 transmits 16 ODU1, or four ODU2, or other combinations in this range, where,
one ODU2 is equivalent to four ODU1.
TDM includes two cases: ODU1 multiplexing to ODU2, and ODU1/ODU2 multiplexing to
ODU3.
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OTN Introduction
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P-15
ODU1floats in ¼ of the OPU2 payload area. An ODU1 frame will cross multiple ODU2
frame boundaries.
A complete ODU1 frame(15296 bytes) requires the bandwidth of (15296/3808 =) 4.017
ODU2 frame
The figure shows the ODU1 frame, including the frame alignment overhead and all-zero
OTUk overhead. The ODU1 adapts to the clock synchronization of the ODU2 signal
through the asynchronous mapping.
As shown in the frame structure in the figure, four ODU1 after adaptation is multiplexed
to the OPU2 payload area in the byte interleaved mode; JC and NJO are inserted to OPU2
overhead area.
After ODU2 overhead is added, ODU2 is mapped to OTU2 (or OTU2V). After OTU2 (or
OTU2V) overhead, frame alignment overhead, and FEC area are added, the OTU2 signals
transmitted through the OTM are formed.
The frame size of ODU1 and ODU2 are the same, that is, 4 lines and 3824 columns, where,
the payload is 3808 column. How can OPU2 take four ODU1 frames? The ODU1 frame
must cross one ODU2 frame border, occupying 3824/3808, that is, 1.004 ODU2 frame.
The frame frequency of the ODU1 differs from that of ODU2. The frame frequency of the
ODU2 is higher than ODU1. Therefore, it is feasible when ODU1 is multiplexed to ODU2
with occupying one ODU2 frame.
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OTN Introduction
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Objectives for this chapter:
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List the overheads in OTN frame;
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Describe the function of each overhead.
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P-16
OTN Introduction
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P-17
The OPUk is in the area from row 15 to row 3824, where, OPUk overhead area is from
column 15 to column 16, OPUk payload area is from column 17 to column 3824,
customer signals are in the OPUk payload area.
The ODUk is in the block structure with 4 lines and 3824 columns, which is composed of
ODUk overhead and OPUk, where ODUk overhead area is from row 1 to row 4 and from
column 1 to column 14. The frame alignment overhead area is from column 1 to column 7
in the first line. Column 8 to 14 in the first line are all-zero.
The OTUk overhead area is from column 8 to column 14 in the first line, and the FEC area
is from column 3825 to column 4084 (256 columns in total) on the right of the frame. The
frame alignment overhead area is from Column 1 to column 7 of the first line in the frame
header.
The customer signal rate corresponding to OTU1/2/3 is respectively 2.5G/10G/40Gbits/s.
The OTUk frame structure of each level is the same. The OTUk signals at the ONMI must
have the sufficient bit timing information. Therefore, the OTUk provides the scramble
function, to construct an appropriate bit pattern by using a scrambler, with the avoidance
of long “1” or long “0” series. With the consideration of the framing, the OTUk overhead
FAS should not be scrambled. The scrambling operation is performed after FEC calculation
and insertion of OTUk signals.
The transmission sequences of the bytes in the OTUk frame is from left to right, from top
down
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OTN Introduction
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P-18
The figure shows the overall electrical layer overhead, include frame alignment overhead,
OTUk layer overhead, ODUk layer overhead, and OPUk layer overhead.
The frame alignment overhead is used for the framing. It is composed of 6-byte frame
alignment signal overhead FAS and 1-byte multi-frame alignment overhead MFAS.
OTUk layer overhead supports the transmission operation function connected through one
or more optical channel. It is composed of 3-byte SM, 2-byte GCC0, and 2-byte RES. It is
terminated at the OTUk signal assembly and dissemble places.
ODUk layer overhead is used to support the operation and maintenance of the optical
channel. It is composed of 3-byte PM for end-to-end ODUk channel monitoring, 6-level
TCM1-TCM6 with 3 bytes respectively, 1-byte TCMACT, 1-byte FTFL, 2-byte EXP, 2-byte
GCC1, 2-byte GCC2, 4-byte APS/PCC, and 6-byte reservation overhead. The ODUk
overhead is terminated at the ODUK assembly and disassemble places. TC overhead is
added at the source, and is terminated at the sink.
OPUk overhead is used to support the customer signal adaptation. It is composed of 1byte PSI, 3-byte JC, 1-byte NJO, and 3-byte reservation overhead. It is terminated at the
OPUk assembly and disassemble places.
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OTN Introduction
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P-19
Frame Alignment Signal (FAS) is used for the frame alignment and positioning, with the
length of six bytes. It is located in Column 1 to Column 6 of Line 1. The contents are
shown in the figure: three OA1 plus three OA2 series. The value of OA1 is 0xF6, and the
value of OA2 is 0x28.
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OTN Introduction
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P-20
Multi-Frame Alignment Signal (MFAS) follows the FAS. Some OTUk and ODUk overheads,
for example, TTI, should cross multiple OTUk/ODUk frames. These overheads must
implement the OTUk/ODUk frame alignment and multi-frame alignment processing. The
MFAS is used for the multi-frame alignment.
The length of the overhead is one byte, and is located in Line 1 Column 7.
The value of the MFAS bytes increases with the increase of the OTUk/ODUk basic frame
number, from 0 to 255 (with up to 256 basic frames). For the overhead of each multiframe structure, the length can be adjusted. For example, if an overhead uses the multiframe structure with 16 basic frames, bit1-bit4 are not calculated when the multi-frame
signals are extracted.
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OTN Introduction
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P-21
The SM overhead is composed of three bytes.
The trail trace identifier (TTI), with the length of one byte, is located in the first byte of the
SM overhead. It is used to transmit 64-byte OTUk-level trail trace identifier signals. The
content sequence of 64 bytes are:
Byte 0 includes SAPI[0] character, with the fixed value of all zeroes.
Byte 1-byte5 include 15-character SAPI.
Byte 16 includes DAPI[0] character, with the fixed value of all zeroes.
Byte 17-byte 31 include 15-character DAPI.
Byte 32- byte 63 are the contents designated by the operator.
The 64-byte TTI signal should align with the OTUk multi-frame. Transmit for four times in
each multi-frame. Each multi-frame contains 256 frames.
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OTN Introduction
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P-22
Bit Interleaved Parity-8 (BIP-8) byte is used for the detection of the OTUk-level bit error
detection. The code is in the even parity inserted among bits. Its length is one byte,
located in the second byte of the SM overhead. For BIP8 parity, calculate the bit in the
whole OPUK frame area of the No.i OTUk frame to obtain the OTUk BIP-8. Insert the
results to No.(i+2) OTUk frame OTUk BIP-8 overhead position. In No.(i+2) frame, as shown
in the figure, compare this value with the DIP8 calculation results of the current frame. If
both values mismatch, detect the bit error block of the near end.
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OTN Introduction
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P-23
Backward Error Indication (BEI) and Backward Incoming Alignment Error (BIAE) are used to
return the detected bit errors to the upstream of the OTUk-level and to introduce the IAE.
The length is four bits. It is located in the most significant four bits of the third byte of the
SM overhead. In the IAE status, the field is set to 1011. The bit error number and non IAE
state is omitted, insert the bit error number (0-8). Other six values may be caused by some
irrelevant status. It should be explained as 0 bit error and BIAE inactivation.
The backward defect indication (BDI) is used for OTUk-level to return the signal invalidity
status detected in the terminal sink function. The length is one bit. It is located in Bit5 of
byte3 of the SM overhead. When the BDI is set to 1, it indicates OTUk backward defect.
Otherwise, it is set to 0.
The Incoming Alignment Error (IAE) is used for the OTUk-level S-CMEP at the ingress point
to notify the peer S-CMEP at the egress point that the alignment error is detected in the
introduction signals. The S-CMEP egress point can use this information to stress the bit
error number. These bit error may be caused by the ODUk frame phase change at the TC
ingress point. The IAE length is one bit. It is located in bit6 of byte 3 of the SM overhead.
The IAE bit is set to 1 to indicate the frame alignment error. Otherwise, it is set to 0.
The last two bits of the SM is reserved, and is set to “00”.
S-Connection Monitoring End Point (CMEP): Section-Connection monitoring end-points
represent end points of trails and correspond as such with the trail termination functions.
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OTN Introduction
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P-24
General Communication Channel 0 (GCC0) is used to support the general communication
between OTUk terminals. The length is two bytes. It is located in Column 11 to Column 12
of line 1. The GCC0 is the transparent channel. The format specification is not discussed
here in this course.
Then, it is the 2-byte OTUk reserved overhead, for the international standardization. It is
located in column 13-column 14 of line 1. The reserved overhead is set to all zeroes.
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OTN Introduction
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P-25
The PM is similar to the SM.
The PM overhead is composed of three bytes. It is located in column 10-column 12 of line
3. The PM is composed of 1-byte TTI, 1-byte BIP-8, 4-bit BDI, 1-bit BEI, and 3-bit STAT.
The definitions of TTI / BIP-8 / BEI / BDI are similar to those in SM. These parts support the
channel monitor.
The PM overhead does not support IAE and BIAE function. In addition, BIP-8 of the PM
overhead is parity of the whole OPUk frame (column 15- 3824). But, the parity position is
in the PM overhead, which differs from the BIP regenerated node in the BIP8.The BEI field
needs not to support the BIAE function. Therefore, one value is less that of the SM
overhead to indicate the return of the IAE state. Four bits of BEI fields in the PM overhead
have nine effective values in total. 0-8 indicates 0-8 bit errors respectively. The other seven
values are caused by some irrelevant status, which can be interpreted as 0 bit error.
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OTN Introduction
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P-26
The STAT field is used for the maintenance signals of ODUk channel level. The length is 3
bits. It is located in the least significant 3 bits of Column 12 of Line 3.
The table describes the meaning of the STAT field.
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OTN Introduction
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P-27
The ODUk overhead defines TCM1-TCM6 of six domains. The Tandem Connection
Monitoring (TCM) overhead supports the monitoring of the ODUk connection. It is used to
the scenarios such as one or more optical UNI to UNI, NNI to NNI serial line connection
monitoring, linear and ring protection switch sub-layer monitoring, the fault location of
the optical channel serial line connection, and the service delivery quality acceptance.
TCM6-TCM1 are located in Column 5-Column 13 of line 2, Column 1-Column 9 of Line 3.
Its format is similar to the SM of the OTUk overhead and the PM of the ODUk overhead.
TTIi / BIP-8i / BEIi / BIAEi / BDIi support the TCMi sub-layer monitoring, where, i ranges
from 1 to 6. The definitions and functions of these parts are the same as the
corresponding parts in SM. But, only the monitoring levels are different.
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OTN Introduction
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P-28
STAT is used for the maintenance signal of TCMi sub layer, whether the IAE error exists in
the source TC-CMEP, whether the source TC-CMEP is activated. The length is 3 bits. It is
located in the least significant 3 bits of the TCMi field.
It indicates the meaning of the STAT field.
TCMi overhead has more BIAE function than PM overhead. In the maintenance signals in
the STAT field, there are more two meanings: No source TC, and TC in use but with IAE
error.
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OTN Introduction
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P-29
Along one ODUk trail, the monitored connections range from 0 to 6. The monitored multilevel connections can be overlay, nesting, or cascading. At present, the overlay mode is
applicable to the test only. Each TC-CMEP inserts or extracts the TCM overhead from six
TCMi overhead domains. The corresponding network operator, network management
system or switching control platform provides the TCMi overhead domain contents.
As shown in the figure, the monitored connects A1-A2, B1-B2, and C1-C2 are nested, A1A2 and B3-B4 are nested, B1-B2 and B3-B4 are cascaded.
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OTN Introduction
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P-30
As shown in the figure, the monitored connects B1-B2 and C1-C2 are overlaid, A1-A2 and
B1-B2 are nested, A1-A2 and C1-C2 are nested.
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OTN Introduction
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P-31
GCC1 and GCC2 can be used to access to the ODUk frame structure (that is, located in 3R
regeneration points) between any two NEs. The length is 2 bytes, respectively located in
Column 1-2 and Column 3-4 of Line 1. It is the transparent channel. Its function is similar
to OTUk overhead GCC0. The ESC function can be applied to the product.
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OTN Introduction
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P-32
The OPUk overhead defines 1-byte payload structure identifier (PSI) overhead to transmit
the 256-byte PSI to indicate the OPUk signal type. The PSI overhead is in Column 15 of
Line 4. The 256-byte PSI signal aligns with the ODUk multi-frame. PSI[0] is a 1-byte
payload type (PT); PSI[1]-PSI[255] are used for the mapping and cascading; PSI[1] is
reserved, and PSI[2]-PSI[17] is the multiplex structure identifier (MSI). The MSI includes the
ODU type and transmitted ODU tributary port number information. For OPU2, there are
only four ODU1 tributary port number. Therefore, only four bytes PSI[2]-PSI[5] are needed,
and the last 12 bytes of the MSI are set to 0.
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OTN Introduction
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P-33
The OOS is the non-associated overhead, which is transmitted through the OSC. The
optical layer overhead function should comply with the standard. The recommendation
defines overheads and corresponding functions contained in the optical layer, and does
not define the frame rate or frame structure. The optical layer overhead include OTS, OMS,
OCh overheads, and generic management information overhead defined by the supplier,
where,
The OTS overhead is used to support the maintenance and operation function of the
optical transmission section, and is terminated at the OTM signal assembly and dissemble
places, including:
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TTI: Transmit the TTI consisting of 64-byte character string. The TTI includes the
source access point indication, destination access point indication, and information
designated by the operator.
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BDI-P: Transmit the OTSn payload signal invalidity status detected from the OTSn
terminal sink function to the upstream.
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BDI-O: Transmit the OTSn overhead signal invalidity status detected from the OTSn
terminal sink function to the upstream.
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PMI: It is used to transmit the status of payload that is not added at the upstream
of the OTS signal source terminal to the downstream, to suppress subsequent
reporting of loss of signal.
To be continued in the next page
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OTN Introduction
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Objectives for this chapter:
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List the maintenance signals type;
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Describe the function and application of maintenance signals.
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OTN Introduction
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OTS, OMS, OCh are all optical layer trails and OTUk, ODUk, Client are all electrical layer
trails.
OSC trail is independent, which is related to supervisory signal.
OTUK use SM section to send maintenance signals.
ODUK use PM and TCM to send maintenance signals.
OTS,OMS,OCh ,OSC send different optical layer maintenance signals.
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OTN Introduction
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OCh client trail sets the source/sink port at the client side of OTU. LQG, as an example, it
is GE service trail of the client port.
OCh trail sets the source/sink port at the WDM side of OTU. LQG, as an example, it is the
wavelength trail.
OMS trail sets the source/sink port at the OUT/IN port of MUX/DeMUX. It is a trail of the
multiplex signal.
OTS trail is the fiber connection between adjacent OM/OD/OA in the main path.
OSC trail is independent, which is related to supervisory signals.
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OTN Introduction
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For the framing and monitoring, the OTUk and ODUkP support to obtaining the LOF and
LOM through the detection of the FAS and MFAS. The ODUkP is applicable to the scenario
from the low-level ODU multiplexing to the high-level ODU signals.
For the continuity monitoring, three layers support the TTI signals of the corresponding
level.
For the information maintenance, three layers support AIS, BDI, and BEI signals. The ASI of
the OTUk layer is the generic AIS signal. In ODUkP and ODUkT, there are all-1 AIS signals.
ODUkP and ODUkT layers support OCI and LCK signals.
The ODUkT layer supports the LTC signals. Note: LTC indicates there is no TCM source.
OTUk and ODUkT support the IAE/BIAE signals.
For the monitoring of the signal quality, three layers support the performance detection
based on the BIP-8 calculation. That is, check the OPUk frames. But the check location and
layers are different.
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OTN Introduction

Objectives for this chapter:

Classify the alarms into the corresponding layer;
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Outline the suppression mechanism of alarms.
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P-38
OTN Introduction
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P-39
Firstly,about the OTN alarm of each electrical layer, for the alarms of OTUk layer, except
the BEFFEC_EXC alarm related to the FEC, other alarm names start with “OTUk”. For the
ODUkP layer, except ODUk_LOFLOM, other alarms start with “ODUk_PM”. For ODUkT
layer alarms, the name starts with “ODUk_TCMi”. The OPUk layer alarm starts with
“OPUk”.
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OTN Introduction
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This table lists OTN performance events in the OTUk, ODUk_PM, and ODUk_TCMi layers.
For definitions related to the performances, see ITU-T G.8201.
ES: Errored Second: When one or more bit error blocks are found in one second, it is called
ES. FEES: far end ES.
SES: Severely Errored Second: In one second period, include ≥ 15% bit error blocks, or,
there is at least one defect (OCI/AIS/LCK/IAE/LTC/TIM/PLM). FESES: far end severely errored
second.
SESR: Severely Eroded Second Ratio: It indicates the ratio between the SES and total
seconds in the available time within the fixed test interval. FESESR: far end Severely Eroded
Second Ratio.
BBE: Background Block Error: It indicates the bit error block beyond the severely eroded
second. FEBBE: far end background block error.
BBER: Background block error ratio. It indicates the ratio between the BBE and total blocks
in the available time within the fixed test interval. The total number of the blocks excludes
the number of the blocks in the SES. FEBBER: far end background block error ratio.
UAS: Unavailable second: It starts from 10 consecutive SES events. The 10 seconds are
considered as a part of the unavailable second. The new available time period starts from
10 consecutive non-SES events. Ten seconds can be considered as one part of the available
time. FEUAS: Far end unavailable second.
IAES: Incoming Alignment Error Second: When the IAE error exists in one second, the
second is the incoming alignment error second. BIAES: backward Incoming Alignment
Error Second.
After the FEC is used, the definitions of all performance events are after the FEC. That is,
the detection of the performance event (for example, BBE and SES) is after all error
corrections.
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OTN Introduction
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Which kinds of the components does the OTM-n.m have?
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OTSn, OMSn, OCh, OTUk/OTUkV, ODUk, OPUk
What’s the difference between SM and PM?
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SM is in the OTUk OH,PM is in the ODUk OH.
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SM contains TTI/BIP-8/BEI/BIAE/BDI/IAE/RES,PM contains TTI/BIP-8/BEI/BDI/STAT.
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OTN Introduction
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OTN Introduction
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FAS
Frame Alignment Signal
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FDI
Forward Defect Indication
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FEC
Forward Error Correction
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GCC
General Communication Channel
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IAE
Incoming Alignment Error
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IrDI
Inter-Domain Interface
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JOH
Justification Overhead
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MFI
Multi-frame Indicator
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MSI
Multiplex Structure Identifier
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NNI
Network Node Interface
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OCC
Optical Channel Carrier
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OCG
Optical Carrier Group
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OCGr
Optical Carrier Group with reduced functionality
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OCh
Optical channel with full functionality
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OChr
Optical channel with reduced functionality
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OCI
Open Connection Indication
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ODTUG
Optical channel Data Tributary Unit Group
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ODTUjk
Optical channel Data Tributary Unit j into k
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ODU
Optical Channel Data Unit
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ODUk
Optical Channel Data Unit-k
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OMS
Optical Multiplex Section
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OMU
Optical Multiplex Unit
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P-43
OTN Introduction
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OTUk
completely standardized Optical Channel Transport Unit-k
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OTUkV
functionally standardized Optical Channel Transport Unit-k
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PCC
Protection Communication Channel
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PLD
Payload
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PMI
Payload Missing Indication
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PRBS
Pseudo Random Binary Sequence
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PSI
Payload Structure Identifier
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PT
Payload Type
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RES
Reserved for future international standardization
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SAPI
Source Access Point Identifier
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Sk
Sink
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SM
Section Monitoring
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So
Source
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TCM
Tandem Connection Monitoring
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TS
Time Slot
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TxTI
Transmitted Trace Identifier
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UNI
User-to-Network Interface
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OTN Introduction
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