What are the main differences between FP LD and DFB LD

I've asked this question before, you see.

The spectral width of DFB lasers is generally relatively narrow, about 10MHz, or even the order of Khz, while the spectral width of FP lasers is relatively wide, and it is a multi-longitudinal mode laser, and the spectral width is generally at the nm level, that is, hundreds of GHz.

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What is CDCD is the abbreviation of Compact Disc in English, which means laser record, and its diameter is 12 cm. Laser discs (LDs) and CDs are often referred to collectively as compact discs. The main differences between them are:

The image part of the laser disc is recorded in analog mode, and its sound part is recorded in analog or mixed analog and digital mode; CD-type sound and images are all recorded digitally. In terms of function, CD is mainly used to record and play back sound, while LD is mainly used to record and play back images.

What is VCD

VCD is the abbreviation of English video compact disc, which translates into Chinese"Compressed platter", actually, it is"Discs"。It is the same size as an ordinary CD, and there is no difference in structure, except that it is stored with film and television programs, and the studio is known as a common name"Video discs", and because it is smaller than the LD video disc used on the laser disc player, it is also called"Small DVD"。Its audio** quality is better than that of a videotape, but slightly worse than that of a large disc.

What is ***

The full name of the English is Digital Video Disk, that is, digital ** disc or digital video disc, which uses MPEG2 compression technology to imitate and store images. It is also known as Digital Versatile Disk, which is a digital multi-purpose disc, which integrates computer technology, optical recording technology and film and television technology, etc., and its purpose is to meet people's needs for large storage capacity and high-performance storage. CD-ROM has not only been widely used in the field of audio technology, but also will drive the development of publishing, broadcasting, communications, www and other industries.

It is very versatile, as can be seen in the five specifications it sets:

ROM - a computer software read-only CD-ROM that is used similarly to a CD ROM;

Video - home audio and video discs, similar to LD or Video CD;

audio - **platter, similar to **cd;

r (or *** write once) - *** written once, similar to cd r;

RAM (or *** rewritable) – a disc that can be read and written multiple times, similar to MO.

Resources.

The full name is Digital Versatile Disc

The full name of CD is Compact Disk, which is a kind of laser high-rent round storage**.

CD is an abbreviation for Compact Disc, Compact Disc.

The main difference between FOB and FCA is that the applicable shipping methods are different. FOB is only applicable to sea freight, while FCA is applicable to any mode of transportation.

FOB is one of the terms commonly used in international **, and the full text of FOB is Free On Board, that is, Free on Board (designated port of shipment), which is customarily called Free on Board at the port of shipment. The cargo can be loaded onto the ship.

FCA: Buyer bears the freight, at the risk. Free carrier.

FOB: As long as the goods are loaded on the ship, the seller is not obligated to bear any risk. Regardless of the designated freight forwarder or designated ship.

FCA: The goods need to be delivered to the freight forwarder or shipping company designated by the buyer.

p s: present value.

The present value is the current value of the capital (generally represented by the letter P, divided into the present value of simple interest and the present value of compound interest).

Conditions of the NPV Law:

Risk definitions and measures are not considered; or think of cash flow as a definite and consistent amount; Or set an expected cash flow and expected rate of return.

1. The mode of transportation of FCA and FOB is different: FOB is only suitable for sea mode of transportation, while FCA is suitable for any mode of transportation.

2. FCA and FOB delivery locations are different: FOB mode transportation is delivered at the transshipment port, and FCA transportation needs to be delivered at the place specified in the contract.

3. The risk division boundary between FCA and FOB is different: the risk division boundary between FOB and the buyer and seller is on the side of the ship at the port of shipment, and the FCA is delivered at the designated delivery location.

4. The transport documents used by FCA and FOB are different: FOB will only be a sea bill of lading, while the transport bill of lading used by FCA depends on different modes of transportation.

5. The provisions of FCA and FOB on the burden of loading and unloading charges are different: in the case of chartering, FOB has the deformation of the term in order to solve the burden of loading and unloading charges, while the FCA does not need to produce the deformation of the term in order to solve the burden of loading and unloading charges.

The main difference between FOB and FCA is that FOB is only suitable for sea freight, while FCA is suitable for any mode of transportation. The other differences need not be discussed.

Signing can be different. FOB wants bill of lading, ON board bill of lading, FCA can sign FCR.

Fees: It stands to reason that in the case of the FCA, the shipper can not pay the terminal fee. However, most of the domestic shipper pays.

The division of responsibilities is not the same.

If there is a core difference, it is the performance difference, and the programming of the two platforms cannot be determined who is good and who is bad, because each has the corresponding needs of a specific group. But the most obvious is the superiority of Linux performance, and Windows because of its kernel-level graphics characteristics, its performance is far inferior to that of Linux, which has a character interface. More importantly, in the long run, the development of Windows must not be as good as Linux, to know how many people are dedicated to the development and maintenance of Linux, if you want you can join it at any time, and Windows is just a closed portal, of course, it cannot be denied that Microsoft is a monopoly in terms of graphics users, and it is difficult to surpass Linux in terms of the number of users.

The Linux kernel does not come with a graphical interface, while the Windows kernel comes with a graphical interface.

FTTH fiber-to-the-home (FTTH) has two categories: Point-to-Point (P2P) and PON (Passive Optical Network). On the surface, the PON structure can save fiber and laser devices. However, because PON is a time-division method, the rate of the device is required to increase with the increase of the ratio of PON, and in the case of a relatively large ratio, it is necessary to use a high-speed DFB-LD, which is 5-10 times that P2P uses a low-speed FP-LD, and at the same time, there is also an electronic module for ranging, and the cost of the device is high, and the gains outweigh the losses.

However, on the other hand, PON can save pipelines and reduce construction, which is more economical and simpler. As a result, more and more PON is being adopted. We often use Fiber's for fiber optic cables.