What causes PMD?
The major cause of PMD is the asymmetry of the fibre optic strand. This asymmetry is caused by the fibre core being slightly out-of-round, or oval. Fibre asymmetry may be inherent in the fibre from the manufacturing process, or it may be a result of mechanical stress on the deployed fibre. The inherent asymmetries of the fibre are fairly constant over time, while the mechanical stress due to movement of the fibre can vary, resulting in a dynamic aspect to PMD. PMD problems with the network can be tricky to tie down because of the dynamic nature of this problem.
 

Delivering voice, data, and video services over next generation fibre optic networks requires efficient testing to ensure network performance, especially at higher data rates, where dispersion can radically impair performance.

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Our PMD/CD Test Equipment
The equipment we use for testing PMD allows allows our technicians to accurately measure both chromatic dispersion (CD) and polarization mode dispersion (PMD) in the C + L bands, in fibre spans of up to 200 km. The DTM improves CD measurement accuracy with the ability to measure CD at 50 different wavelengths. We still however require to plug in the DTM (Dispersion Test Module) source at one end of the link to be tested, connect the receiver at the other, and can start a complete dispersion measurement of the single-mode fibre.
 

Highlights
Our Tester measures both CD and PMD dispersion, cutting the cost and time to our customer

High dynamic range (40 dB) to test over longer distances and temporal precision

Test through amplifiers for extended range

Also our instrument analyses both C and L bands at one time.
 

Our DWDM & CWDM Test Equipment
Successful delivery of voice, data, and video services over existing broadband and telecom networks requires efficient, cost-effective testing solutions. The test tools include a Tunable Laser Source (TLS) with wavelength conversion capabilities. The xWDM module is the first tool to integrate both a tunable laser and a tunable filter, where we can test up to 96 channels with a single instrument.
This second-generation Optical spectrum analyzer, has a wider wavelength spectrum analysis range and increased range, is designed specifically to test dense and coarse wavelength multiplexed (DWDM, CWDM) networks that increasingly dominate interoffice transport. Our xWDM equipment goes beyond network monitoring, and allows our service engineers to test individual channels using signal drop and insert techniques on live lines.
 

Highlight
Optical spectrum analyzer for O, E, S, C, and L bands
Power level, wavelength, and OSNR for each optical signal
Dual ports for monitoring on both sides of a network element
Integrated tunable laser source with modulation (up to 40 Gbps) for adding a channel to a DWDM network
Integrated tunable channel drop is used to separate a single channel from the DWDM signal for BER and protocol analysis with STT SONET/SDH and Ethernet testers

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"Why should I measure loss with an optical loss test set (OLTS) when an optical time domain reflectometer (OTDR) gives me a value for optical loss?" While these instruments seem to take similar measurements, they serve different purposes; the choice between them depends largely on the specific needs of end users requirements.

Below, will explain the differences between these instruments, paying attention to the specific applications of each tool and how loss measurements are obtained with each.

We wish to provide customers with a clear picture of what to expect from each tool and thus enable them to decide which is better suited to the job at hand.

OTDR Optical Power, when choosing a model

Dynamic Range
Wavelength	OTDR Power		26	dB	30	dB
850nm	3.5	dB/Km	7.43	Km	8.57	Km
1300nm	1	dB/Km	26.00	Km	30.00	Km
1310nm	0.35	dB/Km	74.29	Km	85.71	Km
1550nm	0.20	dB/Km	130.00	Km	150.00	Km
1625nm	0.15	dB/Km	173.33	Km	200.00	Km
			35	dB	40	dB
			10.00	Km	11.43	Km
			35.00	Km	40.00	Km
			100.00	Km	114.29	Km
			175.00	Km	200.00	Km
			233.33	Km	266.67	Km
			45	dB	50	dB
			12.86	Km	14.29	Km
			45.00	Km	50.00	Km
			128.57	Km	142.86	Km
			225.00	Km	250.00	Km
			300.00	Km	333.33	Km
The above values are based on fibre loss alone against OTDR Power
Typical Loss Budget
Fibre Km	100	x	0.35	dB/Km=		35	dB
Splices	50	x	0.05	dB	=	2.5	dB
Connectors	2	x	0.5	dB	=	1	dB
					OLB Total	38.5	dB
The above loss budget calculates fibre + connectors + splices against the optical OTDR Power i.e. 38.5dB require an OTDR with a min optical power of 40dB or more especially when other issues contributing to the loss in the fibre will have and effect i.e. design, ageing and bending losses. Patch cords The buffer or jacket on patchcords is often colour-coded to indicate the type of fibre used. The strain relief "boot" that protects the fibre from bending at a connector is colour-coded to indicate the type of connection. Connectors with a plastic shell such as SC connectors typically use a colour-coded shell. Standard colour codings for jackets and boots (or connector shells) are shown below: Buffer/jacket colour Corresponds to Yellow single-mode optical fibre Orange multi-mode optical fibre Aqua 10 gig laser-optimized 50/125 micrometer multi-mode optical fibre Grey outdated colour code for multi-mode optical fibre Blue Sometimes used to designate polarization-maintaining optical fibre   Connector Boot Meaning Comment Blue Physical Contact (PC), 0° mostly used for single mode fibres; some manufacturers use this for polarization-maintaining fibre. Green Angle Polished (APC), 8° not available for multimode fibres Black Physical Contact (PC), 0°   Grey, Beige Physical Contact (PC), 0° multimode fibre connectors White Physical Contact (PC), 0°   Red   High optical power. Sometimes used to connect external pump lasers or Raman pumps. Remark: It is also possible that a small part of a connector is additionally colour-coded, e.g. the leaver of an E-2000 connector or a frame of an adapter. This additional colour coding indicates the correct port for a patch cord, if many patch cords are installed at one point. Multi-fibre cables Individual fibres in a multi-fibre cable are often distinguished from one another by colour-coded jackets or buffers on each fibre. The identification scheme used by manufacturers is based on EIA/TIA-598, "Optical Fibre Cable Colour Coding." EIA/TIA-598 defines identification schemes for fibres, buffered fibres, fibre units, and groups of fibre units within outside plant and premises optical fibre cables. This standard allows for fibre units to be identified by means of a printed legend. This method can be used for identification of fibre ribbons and fibre subunits. The legend will contain a corresponding printed numerical position number and/or colour for use in identification. Position Jacket colour Position Jacket colour 1 Blue 13 Blue with black tracer 2 Orange 14 Orange with black tracer 3 Green 15 Green with black tracer 4 Brown 16 Brown with black tracer 5 Slate 17 Slate with black tracer 6 White 18 White with black tracer 7 Red 19 Red with black tracer 8 Black 20 Black with yellow tracer 9 Yellow 21 Yellow with black tracer 10 Violet 22 Violet with black tracer 11 Rose 23 Rose with black tracer 12 Aqua 24 Aqua with black tracer  Fibre Optic Cable Colour Codes Users have been installing hybrid (MM+SM) cables in the backbone for years. With the premises fibre optic cabling now including two varieties of 50/125 fibre, 62.5/125 and singlemode fibres, managing the cable plant is more difficult. We have already seen instances of users and installers being confused and getting bad test results, as well as having problems with networks operating when connected over the wrong fibre type. There is a colour code standard in process, TIA-598C that addresses this issue, which we could adopt and reference. Here is what it recommends: Coloured outer jackets or print may be used on Premises Distribution Cable, Premises Interconnect Cable or Interconnect Cord, or Premises Breakout Cable to identify the classification and fibre sizes of the fibre. When coloured jackets are used to identify the type of fibre in cable containing only one fibre type, the colours shall be as indicated in Table 3. Other colours may be used providing that the print on the outer jacket identifies fibre classifications in accordance with subclause 4.3.3. Such colours should be as agreed upon between manufacturer and user. Unless otherwise specified, the outer jacket of premises cable containing more than one fibre type shall use a printed legend to identify the quantities and types of fibres within the cable. Table 3 shows the preferred nomenclature for the various fibre types, for example "12 Fibre 8 x 50/125, 4 x 62.5/125." When the print on the outer jacket of premises cable is used to identify the types and classifications of the fibre, the nomenclature of Table 3 is preferred for the various fibre types. Distinctive print characters for other fibre types may be considered for addition to Table 3 at some future date. Fibre Type  Colour Code    Non-military Applications  Military Applications  Suggested Print Nomenclature Multimode (50/125) (TIA-492AAAB) (OM2)  Orange  Orange  50/125 Multimode (50/125) (850 nm Laser-optimized) (TIA-492AAAC) (OM3)  Aqua  Undefined   850 LO 50 /125 Multimode (62.5/125) (TIA-492AAAA) (OM1)  Orange  Slate  62.5/125 Multimode (100/140)  Orange  Green  100/140 Single-mode(TIA-492C000 / TIA-492E000) (OS1, OS2)  Yellow  Yellow  SM/NZDS, SM Polarization Maintaining Single-mode  Blue  Undefined  Undefined (2) NOTES: 1) Natural jackets with coloured tracers may be used instead of solid-colour jackets. 2) Because of the limited number of applications for these fibres, print nomenclature are to be agreed upon between manufacturer and enduser 3) Other colours may be used providing that the print on the outer jacket identifies fibre classifications per sub clause 4.3.3. 4) For some Premises Cable functional types (e.g., plenum cables), coloured jacketing material may not be available. Distinctive jacket colours for other fibre types may be considered for addition to Table 3 at some future date. Connector Colour Codes: Since the earliest days of fibre optics, orange, black or gray was multimode and yellow singlemode. However, the advent of metallic connectors like the FC and ST made colour coding difficult, so coloured boots were often used. The TIA 568 colour code for connector bodies and/or boots is Beige for multimode fibre, Blue for singlemode fibre, and Green for APC (angled) connectors.