L + + waveband amplifier

Abstract

Embodiments of the present disclosure relate to L + + band amplifiers, which may include an optical amplifier system including an erbium-doped fiber amplifier. Embodiments may also include a C-band amplified spontaneous emission stage configured to generate C-band light. Embodiments may also include an L-band stage configured to generate L-band light. Embodiments may also include a Raman amplifier including an optical fiber segment. According to various embodiments, a Raman amplifier may be pumped using a portion of the generated C-band light.

Description

Technical Field

[0001] The present disclosure relates generally to L++ band amplifiers. Background Art

[0002] Aspects of the present invention relate to L++ band amplifiers. Conventional solutions for L++ band amplifiers may have a variety of problems. In this regard, conventional systems and methods for L++ band amplifiers are costly, bulky, and / or inefficient.

[0003] By comparing these methods with some aspects of the present methods and systems as described in the remainder of this disclosure with reference to the accompanying figures, limitations and disadvantages of conventional systems and methods will become apparent to those skilled in the art. Summary of the invention

[0004] Shown in and / or described in connection with at least one of the drawings, and more fully set forth in the claims, is an L++ band amplifier.

[0005] These and other advantages, aspects and novel features of the present disclosure, as well as details of illustrated embodiments thereof, will be more fully understood from the following description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The various features and advantages of the present invention may be more readily understood by reference to the following detailed description taken in conjunction with the accompanying drawings, wherein like reference numerals represent like structural elements.

[0007] Figure 1 is a block diagram illustrating an optical amplifier system according to some embodiments of the present disclosure.

[0008] Figure 2 An exemplary hybrid optical amplifier is shown, comprising a Raman amplifier including an optical fiber segment and an EDFA including a C-band stage and an L-band stage.

[0009] Figure 3 An exemplary gain v wavelength graph is shown.

[0010] Figure 4 An optical hybrid amplifier including a gain flattening filter is shown.

[0011] Figure 5 An optical hybrid amplifier including a pump amplifier is shown.

[0012] Figure 6 An optical hybrid amplifier including a channel filter is shown.

[0013] Figure 7 shows the use of a forward pumping configuration with Figure 2The optical hybrid amplifier in is similar to the optical hybrid amplifier.

[0014] Figure 8 shows the use of a forward-backward pumping configuration with Figure 7 The optical hybrid amplifier in is similar to the optical hybrid amplifier.

[0015] Fig. 9 The system includes a distributed Raman amplifier and a discrete Raman amplifier. Figure 2 The optical hybrid amplifier is similar to the optical hybrid amplifier.

[0016] Fig.10 A Raman pump unit (RPU) 150 is shown with Fig. 9 The optical hybrid amplifier is similar to the optical hybrid amplifier.

[0017] Fig.11 An optical hybrid amplifier including a high-order pump is shown. DETAILED DESCRIPTION

[0018] The following discussion provides different examples of methods and systems for L++ band amplifiers. Such examples are non-limiting, and the scope of the appended claims should not be limited to the specific examples disclosed. In the following discussion, the terms "example" and "for example" are non-limiting.

[0019] The accompanying drawings illustrate the overall manner of construction, in which descriptions and details of well-known features and techniques may be omitted to avoid unnecessarily obscuring the present disclosure. In addition, the elements in the accompanying drawings are not necessarily drawn to scale. For example, the sizes of some elements in the drawings may be enlarged relative to other elements to help improve the understanding of the examples discussed in the present disclosure. The same reference numerals in different drawings represent the same elements.

[0020] The term "and / or" refers to any one or more of the items in a list connected by "and / or". As an example, "x and / or y" means any element in the three-element set {(x), (y), (x, y)}. In other words, "x and / or y" means "one or both of x and y". As another example, "x, y and / or z" refers to any element in the seven-element set {(x), (y), (z), (x, y), (x, z), (y, z), (x, y, z)}. In other words, "x, y and / or z" means "one or more of x, y and z".

[0021] The terms “comprising,” “including,” “including,” and / or “comprising” are “open” terms and specify the presence of stated features but do not preclude the presence or addition of one or more other features.

[0022] The terms "first", "second", etc. may be used to describe various elements in this article, and these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. Thus, for example, the first element discussed in the present disclosure may be referred to as the second element without departing from the teachings of the present disclosure.

[0023] Unless otherwise specified, the term "coupled" may be used to describe two elements that are in direct contact with each other or to describe two elements that are indirectly connected by one or more other elements. For example, if element A is coupled to element B, element A may be in direct contact with element B or indirectly connected to element B through an intermediate element C. Similarly, the terms "over" or "on" may be used to describe two elements that are in direct contact with each other or to describe two elements that are indirectly connected by one or more other elements.

[0024] Embodiments of the present disclosure may include an optical amplifier system including an erbium-doped fiber amplifier including a C-band amplified spontaneous emission stage configured to generate C-band light and an L-band stage configured to generate L-band light. The optical amplifier also includes a Raman amplifier including a fiber span. According to various embodiments, the Raman amplifier can be pumped using a portion of the generated C-band light.

[0025] According to various embodiments, the system may include a pump amplifier that amplifies the portion of the generated C-band light. According to different embodiments, the system may include a channel filter that filters the light used to pump the Raman amplifier. According to various embodiments, the Raman amplifier may be configured to provide its highest gain in the L++ band.

[0026] According to various embodiments, the Raman amplifier can be configured to generate a gain that is complementary to the gain of the erbium-doped fiber amplifier such that the combined gain in the optical amplifier system can be substantially flat in the C-band, L-band, and L++ bands. According to various embodiments, the system can include one or more gain flattening filters.

[0027] According to various embodiments, the one or more gain flattening filters may be configured to shape the gain of the Raman amplifier and / or may be configured to shape the combined gain of the erbium-doped fiber amplifier and the Raman amplifier. According to various embodiments, the Raman amplifier may be a distributed Raman amplifier. According to various embodiments, the system may include discrete Raman amplifier fiber segments. According to various embodiments, the system may include a Raman pump unit.

[0028] The present invention relates to optical amplifiers, and more particularly to an optical amplifier suitable for use as an L++ band amplifier. In recent years, communication systems have steadily used larger bandwidths. In optical communications, over the past 20 years or so, the transmission bandwidth may have increased to about 4.5 THz for each band. Now, the transmission bandwidth may gradually increase to even more than 6 THz. Typically, the bandwidth involved may be referred to as the C-band, approximately for wavelengths from about 1520 nm to about 1575 nm, the L-band for bandwidths corresponding approximately to wavelengths from 1575 nm to about 1616 nm, and the L++-band for bandwidths extending from about 1616 nm to 1626 nm or more.

[0029] Many conventional L-band amplifiers may use erbium-doped fiber amplifiers (EDFAs). However, the gain of conventional erbium-doped fiber amplifiers may decrease rapidly beyond 1616 nm. Physical constraints, such as reduced emission profiles or increased excited-state absorption, may limit the gain and may be difficult to overcome.

[0030] Figure 1 1 is a block diagram depicting an optical amplifier system 100 according to some embodiments of the present disclosure. In some embodiments, the optical amplifier system 100 may include an erbium doped fiber amplifier (EDFA) 110 and a Raman amplifier 120. The EDFA 110 may include a C-band 112 amplified spontaneous emission (ASE) stage configured to generate C-band light and an L-band stage 114 configured to generate L-band light. The Raman amplifier 120 may include an optical fiber segment 122. The Raman amplifier 120 may be pumped using a portion of the generated C-band light.

[0031] EDFA 110 may be an amplifier using an optical fiber including erbium ions (referred to as erbium-doped material). Erbium (Er) may be a rare earth element that may have special optical properties, particularly in terms of its ability to absorb and emit light in the infrared wavelength range. This property makes erbium-doped materials useful in a variety of optical applications, including erbium-doped fiber amplifiers.

[0032] When manufacturing optical fiber, a small amount of erbium ions can be intentionally introduced into the core of the optical fiber. This can be called erbium doping. When these ions in the optical fiber are excited by an external light source (pump light, usually about 980nm or 1480nm) and the input signal light is injected into the optical fiber, the excited erbium ions can release energy in the form of additional photons, which can be in phase and coherent with the input optical signal light, thereby effectively amplifying the input signal without electro-optical conversion. According to various embodiments of the present invention, the EDFA can include multiple amplifier stages operating in different operating bands, namely C-band stage 112 and L-band stage 114.

[0033] Raman amplifier 120 may be another type of optical amplifier used in fiber optic communication systems to amplify optical signals. Unlike erbium doped fiber amplifiers (EDFAs) that rely on the properties of erbium doped materials, Raman amplifiers may utilize Raman scattering phenomena to achieve signal amplification.

[0034] Raman scattering can be a nonlinear optical process in which light can interact with vibrational modes of a material through which it travels. When a pump laser is emitted into an optical fiber, it can generate vibrational modes within the optical fiber material. These modes can interact with incident signal light, causing energy transfer from the pump light to the signal light. Thus, the signal light can be amplified by the Raman scattering process. The optical fiber can be the optical fiber segment 122.

[0035] Raman amplifiers can provide amplification over a wide range of wavelengths and exhibit low noise levels depending on, for example, the pump wavelength, the pump power, the length of the fiber segment 122, and the interaction between the pump wavelength and the input signal wavelength.

[0036] By combining the Raman amplifier 120 with the EDFA 110, a hybrid optical amplifier system 100 can be created. Such a system can combine the relative advantages of the EDFA and the Raman amplifier. According to various embodiments of the present disclosure, the Raman amplifier 120 can extend the amplification bandwidth in the L++ band. In some instances, the L++ or extended L-band can also be referred to as the super L-band. In other words, the hybrid approach can allow for optimized signal amplification across a wider wavelength range while also benefiting from the noise performance and well-established EDFA technology.

[0037] Figure 2 An exemplary hybrid optical amplifier 100 is shown, which includes: a Raman amplifier, which includes a fiber segment 122; an EDFA 110, which includes a C-band stage 112 and an L-band stage 114. According to various embodiments of the present disclosure, a first portion of the light generated by the C-band stage 112 can be fed into the L-band stage 114 of the EDFA 110. A second portion of the light generated by the C-band stage 112 can be fed into the fiber segment 122, where it can act as a pump (by the L-band stage 114) to generate Raman amplification in the fiber segment 122. Figure 2 ). Compared to conventional systems, this arrangement can use the C-band stage 112 of the EDFA 110 as a pump for the Raman amplifier fiber segment 122 and thus can avoid the use of a dedicated Raman amplifier pump unit.

[0038] Figure 3 Illustrative gain v wavelength graphs are shown for A: Raman amplifier 120 (dashed line), B: EDFA 110 (dotted line), C: combined gain of the hybrid amplifier (dash-dot line).

[0039] As can be seen from A, the Raman amplifier 120 can be configured to generate increased gain at larger wavelengths (e.g., at L++ band wavelengths of 1616nm to 1626nm and larger). As can be seen from B, the EDFA 110 can generate greater gain at shorter wavelengths. The gain of the EDFA 110 may drop in the L++ band wavelengths. As can be seen from C, the combined gain of the Raman amplifier 120 stage and the EDFA 110 stage is substantially flat over a range of wavelengths, as shown by the dotted line.

[0040] Figure 4 An optical hybrid amplifier is shown that includes a gain flattening filter 125. The gain flattening filter 125 may be configured to advantageously shape the gain function of the Raman amplifier 120 and / or the EDFA 110. For example, it may be desirable to Figure 3 The Raman 120 gain shown in inset A looks like Figure 3 The vertically flipped version of the EDFA110 gain shown in the inset B of FIG. 1 is used to enable the combined gain to be in the desired wavelength range ( Figure 3 C). The gain flattening filter 125 can help obtain the desired gain v wavelength shape. Before the EDFA 110 and / or within the EDFA 110, such as the L-band stage 114, the gain flattening filter 125 can be used to flatten the combined gain. Thus, in some embodiments, one or more gain flattening filters can be configured to shape the gain of the Raman amplifier 120 and / or can be configured to shape the combined gain of the erbium-doped fiber amplifier 110 and the Raman amplifier 120.

[0041] Figure 5 An optical hybrid amplifier is shown that includes a pump amplifier 130. In some embodiments, the optical amplifier system 100 can include a pump amplifier 130 that amplifies a portion of the generated C-band light. In some instances, it may be desirable to increase the power of the C-band light / fiber segment 122 from the C-band stage 112 used to pump the Raman amplifier 120, as the characteristics of the Raman amplifier 120 may be particularly dependent on the power of the C-band pump light.

[0042] Figure 6 An optical hybrid amplifier including a channel filter 135 is shown. In some embodiments, the optical amplifier system 100 may include a channel filter 135 to filter light used to pump the Raman amplifier 120 / fiber segment 122. For example, the C-band light from the C-band stage 112 may be a broadband emission. In such a case, it may be preferred to selectively pump the Raman amplifier 120 with one or more narrowband signals to obtain favorable filter characteristics for the Raman amplifier 120. Therefore, in this case, the channel filter 135 may have, for example, one or more narrow passbands.

[0043] Figure 7 shows the use of forward pumping and Figure 2 According to various embodiments of the present disclosure, the Raman amplifier 120 may be forward pumped with light from the C-band stage 112, as shown.

[0044] Figure 8 shows the use of a forward-backward pumping configuration with Figure 7 The optical hybrid amplifier in is similar to the optical hybrid amplifier.

[0045] Fig. 9 The system includes a distributed Raman amplifier and a discrete Raman amplifier. Figure 2 A discrete Raman amplifier may be an amplifier in which there is a fiber segment dedicated to Raman amplifiers, such as fiber segment 140. For example, fiber segment 140 may be part of a localized network device. In a distributed Raman amplifier, fiber segment 122 forms part of a communication network. In certain example embodiments, discrete Raman amplifiers or distributed Raman amplifiers or a combination of both may be used.

[0046] Fig.10 Shown with Fig. 9 1. In some instances, it may be advantageous to supplement the pump from the C-band stage 112 with a Raman pump unit (RPU) 150. This may provide, for example, additional power to the distributed Raman amplifier and / or discrete Raman amplifier. Thus, in some embodiments, the Raman pump unit 150 may also be coupled between the fiber segment 140 and the C-band stage 112 (not shown).

[0047] Fig.11 An optical hybrid amplifier including a high-order pump is shown. In some instances, cascaded Raman amplification is desired. For example, a Raman pump unit 150 can generate Raman amplification in the fiber segment 140, which can pump the C-band stage 112. This can increase the power in the C-band stage 112, which in turn can generate Raman amplification together with the fiber segment 140. According to various embodiments, the pumps are typically cascaded from the shortest pump wavelength to the longer pump wavelength. For example, the Raman pump unit 150 can pump at, for example, 1450nm, generate Raman amplification at, for example, 1550nm, and the Raman amplification pumps the C-band stage 112 to generate a stronger signal in, for example, the 1550nm region. This can be referred to as high-order pumping.

[0048] In various example embodiments, Figures 4 to 6 The channel filter 135, gain flattening filter 125 and / or pump amplifier 130 shown may be incorporated into Figures 1 to 11 In any of the embodiments shown. Similarly, discrete Raman amplifiers and / or distributed Raman amplifiers may be used to implement Figures 1 to 11 Any of the embodiments shown in Fig. 9 Similarly, except for pumping from the C-band stage 112, Figures 1 to 11 Any of the embodiments shown in can be implemented using the Raman pump unit 150. In addition, Figure 7 The forward pumping structure and Figure 8 The forward-backward pumping structure can be extended to Figures 1 to 11 Any of the embodiments shown in .

[0049] The present disclosure includes reference to certain examples; however, it will be appreciated by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the present disclosure. In addition, modifications may be made to the disclosed examples without departing from the scope of the present disclosure. Therefore, the present disclosure is not intended to be limited to the disclosed embodiments, but rather the present disclosure will include all examples that fall within the scope of the appended claims.

Claims

1. An optical amplifier system, the system comprising: Erbium-doped fiber amplifier, including: a C-band amplified spontaneous emission stage configured to generate C-band light; An L-band amplifier stage configured to generate L-band light; and A Raman amplifier comprising a segment of optical fiber and wherein a portion of the generated C-band light is used to pump the Raman amplifier. 2 . The system of claim 1 , further comprising a pump amplifier that amplifies the portion of the generated C-band light.

3. The system of claim 1, further comprising a channel filter that filters light used to pump the Raman amplifier.

4. The system according to claim 1, wherein: The Raman amplifier is configured to provide the highest gain of the Raman amplifier in the L++ band.

5. The system according to claim 1, wherein: The Raman amplifier is configured to generate a gain complementary to a gain of the erbium doped fiber amplifier such that a combined gain in the optical amplifier system is flat in the C-band, the L-band, and the L++-band.

6. The system of claim 1, further comprising one or more gain flattening filters.

7. The system according to claim 6, wherein: The one or more gain flattening filters are configured to shape the gain of the Raman amplifier and / or to shape the combined gain of the erbium doped fiber amplifier and the Raman amplifier.

8. The system according to claim 1, wherein: The Raman amplifier is a distributed Raman amplifier.

9. The system of claim 1 further comprising discrete Raman amplifier fiber segments.

10. The system of claim 1, further comprising a Raman pumping unit.

11. The system according to claim 10, wherein: The Raman pump unit includes a high-order pump.

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